def where(condition, x, y, name=None):
  """Return elements from x or y depending on condition.

  See `tf.where` for more details. This function currently only implements the
  three argument version of where.

  Args:
    condition: LabeledTensor of type `bool`.
    x: LabeledTensor for values where condition is true.
    y: LabeledTensor for values where condition is false.
    name: Optional op name.

  Returns:
    The labeled tensor with values according to condition.

  Raises:
    ValueError: if `x` and `y` have different axes, or if the axes of `x` do not
      start with the axes of `condition`.
  """
  with ops.name_scope(name, 'lt_where', [condition, x, y]) as scope:
    condition = core.convert_to_labeled_tensor(condition)
    x = core.convert_to_labeled_tensor(x)
    y = core.convert_to_labeled_tensor(y)

    if not condition.axes == x.axes == y.axes:
      raise ValueError('all inputs to `where` must have equal axes')

    op = array_ops.where(condition.tensor, x.tensor, y.tensor, name=scope)
    return core.LabeledTensor(op, x.axes)

def foldl(fn, labeled_tensor, initial_value, name=None):
  """Left fold on the list of tensors unpacked from labeled_tensor.

  See tf.foldl.

  Args:
    fn: The function to apply to each unpacked LabeledTensor.
      It should have type (LabeledTensor, LabeledTensor) -> LabeledTensor.
      Its arguments are (accumulated_value, next_value).
    labeled_tensor: The input tensor.
    initial_value: The initial value of the accumulator.
    name: Optional op name.

  Returns:
    The accumulated value.
  """
  with ops.name_scope(name, 'lt_foldl',
                      [labeled_tensor, initial_value]) as scope:
    labeled_tensor = core.convert_to_labeled_tensor(labeled_tensor)
    initial_value = core.convert_to_labeled_tensor(initial_value)

    @tc.returns(ops.Tensor)
    @tc.accepts(ops.Tensor, ops.Tensor)
    def tf_fn(accumulator, next_element):
      accumulator_lt = core.LabeledTensor(accumulator, initial_value.axes)
      next_element_lt = core.LabeledTensor(
          next_element, list(labeled_tensor.axes.values())[1:])
      return fn(accumulator_lt, next_element_lt).tensor

    foldl_op = functional_ops.foldl(
        tf_fn, labeled_tensor.tensor, initializer=initial_value.tensor)
    foldl_lt = core.LabeledTensor(foldl_op, initial_value.axes)

    return core.identity(foldl_lt, name=scope)

def boolean_mask(labeled_tensor, mask, name=None):
  """Apply a boolean mask to a labeled tensor.

  Unlike `tf.boolean_mask`, this currently only works on 1-dimensional masks.
  The mask is applied to the first axis of `labeled_tensor`. Labels on the first
  axis are removed, because True indices in `mask` may not be known dynamically.

  Args:
    labeled_tensor: The input tensor.
    mask: The type of the returned tensor.
    name: Optional op name.

  Returns:
    The masked labeled tensor.

  Raises:
    ValueError: if the first axis of the mask
  """
  with ops.name_scope(name, 'lt_boolean_mask', [labeled_tensor, mask]) as scope:
    labeled_tensor = core.convert_to_labeled_tensor(labeled_tensor)
    mask = core.convert_to_labeled_tensor(mask)

    if len(mask.axes) > 1:
      raise NotImplementedError(
          "LabeledTensor's boolean_mask currently only supports 1D masks")
    mask_axis = list(mask.axes.values())[0]
    lt_axis = list(labeled_tensor.axes.values())[0]
    if mask_axis != lt_axis:
      raise ValueError('the first axis of the labeled tensor and the mask '
                       'are not equal:\n%r\n%r' % (lt_axis, mask_axis))
    op = array_ops.boolean_mask(labeled_tensor.tensor, mask.tensor, name=scope)
    # TODO(shoyer): attempt to infer labels for the masked values, by calling
    # tf.contrib.util.constant_value on the mask?
    axes = [lt_axis.name] + list(labeled_tensor.axes.values())[1:]
    return core.LabeledTensor(op, axes)

def concat(labeled_tensors, axis_name, name=None):
  """Concatenate tensors along a dimension.

  See tf.concat.

  Args:
    labeled_tensors: A list of input LabeledTensors.
    axis_name: The name of the axis along which to concatenate.
    name: Optional op name.

  Returns:
    The concatenated tensor.
    The coordinate labels for the concatenation dimension are also concatenated,
    if they are available for every tensor.

  Raises:
    ValueError: If fewer than one tensor inputs is provided, if the tensors
      have incompatible axes, or if `axis_name` isn't the name of an axis.
  """
  with ops.name_scope(name, 'lt_concat', labeled_tensors) as scope:
    labeled_tensors = [
        core.convert_to_labeled_tensor(lt) for lt in labeled_tensors
    ]

    if len(labeled_tensors) < 1:
      raise ValueError('concat expects at least 1 tensor, but received %s' %
                       labeled_tensors)

    # All tensors must have these axes.
    axes_0 = labeled_tensors[0].axes
    axis_names = list(axes_0.keys())

    if axis_name not in axis_names:
      raise ValueError('%s not in %s' % (axis_name, axis_names))

    shared_axes = axes_0.remove(axis_name)

    tensors = [labeled_tensors[0].tensor]
    concat_axis_list = [axes_0[axis_name]]
    for labeled_tensor in labeled_tensors[1:]:
      current_shared_axes = labeled_tensor.axes.remove(axis_name)
      if current_shared_axes != shared_axes:
        # TODO(shoyer): add more specific checks about what went wrong,
        # including raising AxisOrderError when appropriate
        raise ValueError('Mismatched shared axes: the first tensor '
                         'had axes %r but this tensor has axes %r.' %
                         (shared_axes, current_shared_axes))

      # Accumulate the axis labels, if they're available.
      concat_axis_list.append(labeled_tensor.axes[axis_name])
      tensors.append(labeled_tensor.tensor)

    concat_axis = core.concat_axes(concat_axis_list)
    concat_dimension = axis_names.index(axis_name)
    concat_tensor = array_ops.concat(tensors, concat_dimension, name=scope)
    values = list(axes_0.values())
    concat_axes = (values[:concat_dimension] + [concat_axis] +
                   values[concat_dimension + 1:])

    return core.LabeledTensor(concat_tensor, concat_axes)

def unpack(labeled_tensor, axis_name=None, name=None):
  """Unpack the tensor.

  See tf.unpack.

  Args:
    labeled_tensor: The input tensor.
    axis_name: Optional name of axis to unpack. By default, the first axis is
      used.
    name: Optional op name.

  Returns:
    The list of unpacked LabeledTensors.

  Raises:
    ValueError: If `axis_name` is not an axis on the input.
  """
  with ops.name_scope(name, 'lt_unpack', [labeled_tensor]) as scope:
    labeled_tensor = core.convert_to_labeled_tensor(labeled_tensor)

    axis_names = list(labeled_tensor.axes.keys())
    if axis_name is None:
      axis_name = axis_names[0]

    if axis_name not in axis_names:
      raise ValueError('%s not in %s' % (axis_name, axis_names))
    axis = axis_names.index(axis_name)

    unpack_ops = array_ops.unstack(labeled_tensor.tensor, axis=axis, name=scope)
    axes = [a for i, a in enumerate(labeled_tensor.axes.values()) if i != axis]
    return [core.LabeledTensor(t, axes) for t in unpack_ops]

  def encode(self, labeled_tensor):
    """Reshape the input to the target shape.

    If called several times, the axes named in existing_axis_names must be
    identical.

    Args:
      labeled_tensor: The input tensor.

    Returns:
      The input reshaped to the target shape.

    Raises:
      ValueError: If the axes in existing_axis_names don't match the axes of
        a tensor in a previous invocation of this method.
    """
    with tf_ops.name_scope(self._name, 'lt_reshape_encode',
                           [labeled_tensor]) as scope:
      labeled_tensor = core.convert_to_labeled_tensor(labeled_tensor)

      reshape_lt = ops.reshape(labeled_tensor,
                               self._existing_axis_names,
                               self._new_axes,
                               name=scope)

      axes = [labeled_tensor.axes[n] for n in self._existing_axis_names]
      if self._existing_axes is not None and self._existing_axes != axes:
        raise ValueError(
            'input axes %r do not match axes from previous method call %r' %
            (axes, self._existing_axes))
      else:
        self._existing_axes = axes

      return reshape_lt

  def decode(self, labeled_tensor):
    """Reshape the input to the original shape.

    This is the inverse of encode.
    Encode must have been called at least once prior to this method being
    called.

    Args:
      labeled_tensor: The input tensor.

    Returns:
      The input reshaped to the original shape.

    Raises:
      ValueError: If this method was called before encode was called.
    """
    if self._existing_axes is None:
      raise ValueError('decode called before encode')

    with tf_ops.name_scope(self._name, 'lt_reshape_decode',
                           [labeled_tensor]) as scope:
      labeled_tensor = core.convert_to_labeled_tensor(labeled_tensor)

      new_axis_names = [axis if isinstance(axis, string_types) else
                        core.as_axis(axis).name for axis in self._new_axes]

      return ops.reshape(labeled_tensor,
                         new_axis_names,
                         self._existing_axes,
                         name=scope)

def parse_example(serialized, features, name=None, example_names=None):
  """Parse `Example` protos into a `dict` of labeled tensors.

  See tf.parse_example.

  Args:
    serialized: A 1-D LabeledTensor of strings, a batch of binary serialized
      `Example` protos.
    features: A `dict` mapping feature keys to `labeled_tensor.FixedLenFeature`
      values.
    name: A name for this operation (optional).
    example_names: A vector (1-D Tensor) of strings (optional), the names of
      the serialized protos in the batch.

  Returns:
    A `dict` mapping feature keys to `LabeledTensor` values. The single axis
    from `serialized` will be prepended to the axes provided by each feature.

  Raises:
    ValueError: if any feature is invalid.
  """
  serialized = core.convert_to_labeled_tensor(serialized)
  unlabeled_features = _labeled_to_unlabeled_features(features)

  unlabeled_parsed = parsing_ops.parse_example(
      serialized.tensor, unlabeled_features, name, example_names)

  parsed = {}
  for name, parsed_feature in unlabeled_parsed.items():
    axes = list(serialized.axes.values()) + features[name].axes
    parsed[name] = core.LabeledTensor(parsed_feature, axes)

  return parsed

def parse_single_example(serialized, features, name=None, example_names=None):
  """Parses a single `Example` proto.

  See tf.parse_single_example.

  Args:
    serialized: A scalar string Tensor or LabeledTensor, a single serialized
      Example.
    features: A `dict` mapping feature keys to `labeled_tensor.FixedLenFeature`
      values.
    name: A name for this operation (optional).
    example_names: (Optional) A scalar string Tensor, the associated name.

  Returns:
    A `dict` mapping feature keys to `LabeledTensor` values.

  Raises:
    ValueError: if any feature is invalid.
  """
  serialized = core.convert_to_labeled_tensor(serialized)
  unlabeled_features = _labeled_to_unlabeled_features(features)

  unlabeled_parsed = parsing_ops.parse_single_example(
      serialized.tensor, unlabeled_features, name, example_names)

  parsed = {}
  for name, parsed_feature in unlabeled_parsed.items():
    parsed[name] = core.LabeledTensor(parsed_feature, features[name].axes)

  return parsed

def map_fn(fn, labeled_tensor, name=None):
  """Map on the list of tensors unpacked from labeled_tensor.

  See tf.map_fn.

  Args:
    fn: The function to apply to each unpacked LabeledTensor.
      It should have type LabeledTensor -> LabeledTensor.
    labeled_tensor: The input tensor.
    name: Optional op name.

  Returns:
    A tensor that packs the results of applying fn to the list of tensors
    unpacked from labeled_tensor.
  """
  with ops.name_scope(name, 'lt_map_fn', [labeled_tensor]) as scope:
    labeled_tensor = core.convert_to_labeled_tensor(labeled_tensor)

    unpack_lts = unpack(labeled_tensor)

    # TODO(ericmc): Fix this upstream.
    if labeled_tensor.dtype == dtypes.string:
      # We must construct the full graph here, because functional_ops.map_fn
      # doesn't work for string-valued tensors.
      # Constructing the full graph may be slow.
      map_lts = [fn(t) for t in unpack_lts]
      return pack(map_lts, list(labeled_tensor.axes.values())[0], name=scope)
    else:
      # Figure out what the axis labels should be, but use tf.map_fn to
      # construct the graph because it's efficient.
      # It may be slow to construct the full graph, so we infer the labels from
      # the first element.
      # TODO(ericmc): This builds a subgraph which then gets thrown away.
      # Find a more elegant solution.
      first_map_lt = fn(unpack_lts[0])
      final_axes = list(labeled_tensor.axes.values())[:1] + list(
          first_map_lt.axes.values())

      @tc.returns(ops.Tensor)
      @tc.accepts(ops.Tensor)
      def tf_fn(tensor):
        original_axes = list(labeled_tensor.axes.values())[1:]
        tensor_lt = core.LabeledTensor(tensor, original_axes)
        return fn(tensor_lt).tensor

      map_op = functional_ops.map_fn(
          tf_fn, labeled_tensor.tensor, dtype=first_map_lt.dtype)
      map_lt = core.LabeledTensor(map_op, final_axes)

      return core.identity(map_lt, name=scope)

def squeeze(labeled_tensor, axis_names=None, name=None):
  """Remove size-1 dimensions.

  See tf.squeeze.

  Args:
    labeled_tensor: The input tensor.
    axis_names: The names of the dimensions to remove, or None to remove
      all size-1 dimensions.
    name: Optional op name.

  Returns:
    A tensor with the specified dimensions removed.

  Raises:
    ValueError: If the named axes are not in the tensor, or if they are
      not size-1.
  """
  with ops.name_scope(name, 'lt_squeeze', [labeled_tensor]) as scope:
    labeled_tensor = core.convert_to_labeled_tensor(labeled_tensor)

    if axis_names is None:
      axis_names = [a.name for a in labeled_tensor.axes.values() if len(a) == 1]

    for axis_name in axis_names:
      if axis_name not in labeled_tensor.axes:
        raise ValueError('axis %s is not in tensor axes %s' %
                         (axis_name, labeled_tensor.axes))
      elif len(labeled_tensor.axes[axis_name]) != 1:
        raise ValueError(
            'cannot squeeze axis with size greater than 1: (%s, %s)' %
            (axis_name, labeled_tensor.axes[axis_name]))

    squeeze_dimensions = []
    axes = []
    for i, axis in enumerate(labeled_tensor.axes.values()):
      if axis.name in axis_names:
        squeeze_dimensions.append(i)
      else:
        axes.append(axis)

    if squeeze_dimensions:
      squeeze_op = array_ops.squeeze(labeled_tensor.tensor,
                                     squeeze_dimensions,
                                     name=scope)
    else:
      squeeze_op = array_ops.identity(labeled_tensor.tensor, name=scope)

    return core.LabeledTensor(squeeze_op, axes)

def ones_like(labeled_tensor, dtype=None, name=None):
  """Creates an identical tensor with all elements set to one.

  Args:
    labeled_tensor: The input tensor.
    dtype: The type of the returned tensor.
    name: Optional op name.

  Returns:
    The tensor with elements set to one.
  """
  with ops.name_scope(name, 'lt_ones_like', [labeled_tensor]) as scope:
    labeled_tensor = core.convert_to_labeled_tensor(labeled_tensor)
    op = array_ops.ones_like(labeled_tensor.tensor, dtype=dtype, name=scope)
    return core.LabeledTensor(op, labeled_tensor.axes)

def cast(labeled_tensor, dtype=None, name=None):
  """Casts a labeled tensor to a new type.

  Args:
    labeled_tensor: The input tensor.
    dtype: The type of the returned tensor.
    name: Optional op name.

  Returns:
    A labeled tensor with the new dtype.
  """
  with ops.name_scope(name, 'lt_cast', [labeled_tensor]) as scope:
    labeled_tensor = core.convert_to_labeled_tensor(labeled_tensor)
    op = math_ops.cast(labeled_tensor.tensor, dtype=dtype, name=scope)
    return core.LabeledTensor(op, labeled_tensor.axes)

def pad(labeled_tensor, paddings, mode='CONSTANT', name=None):
  """Pads a tensor.

  See tf.pad.

  Args:
    labeled_tensor: The input tensor.
    paddings: A mapping where the keys are axis names and the values are
      tuples where the first element is the padding to insert at the beginning
      of the axis and the second is the padding to insert at the end of the
      axis.
    mode: One of "CONSTANT", "REFLECT", or "SYMMETRIC".
    name: Optional op name.

  Returns:
    A tensor with the indicated axes padded, optionally with those axes extended
    with the provided labels.

  Raises:
    ValueError: If the padded axes are not axes in the input tensor.
  """
  with ops.name_scope(name, 'lt_pad', [labeled_tensor]) as scope:
    labeled_tensor = core.convert_to_labeled_tensor(labeled_tensor)

    if not set(paddings.keys()) <= set(labeled_tensor.axes.keys()):
      raise ValueError('pad axes %r are not contained in the set of axis '
                       'names %r on the input labeled tensor' %
                       (paddings.keys(), labeled_tensor.axes))

    new_axes = []
    padding_pairs = []
    for name, axis in labeled_tensor.axes.items():
      if name in paddings:
        padding_before, padding_after = paddings[name]
        axis_before = core.Axis(name, padding_before)
        axis_after = core.Axis(name, padding_after)
        new_axes.append(core.concat_axes([axis_before, axis, axis_after]))
        padding_pairs.append((len(axis_before), len(axis_after)))
      else:
        new_axes.append(axis)
        padding_pairs.append((0, 0))

    pad_op = array_ops.pad(labeled_tensor.tensor,
                           padding_pairs,
                           mode,
                           name=scope)

    return core.LabeledTensor(pad_op, new_axes)

def random_crop(labeled_tensor, shape_map, seed=None, name=None):
  """Randomly crops a tensor to a given size.

  See tf.random_crop.

  Args:
    labeled_tensor: The input tensor.
    shape_map: A dictionary mapping axis names to the size of the random crop
      for that dimension.
    seed: An optional random seed.
    name: An optional op name.

  Returns:
    A tensor of the same rank as `labeled_tensor`, cropped randomly in the
    selected dimensions.

  Raises:
    ValueError: If the shape map contains an axis name not in the input tensor.
  """
  with ops.name_scope(name, 'lt_random_crop', [labeled_tensor]) as scope:
    labeled_tensor = core.convert_to_labeled_tensor(labeled_tensor)

    for axis_name in shape_map:
      if axis_name not in labeled_tensor.axes:
        raise ValueError('Selection axis %s not in axes %s' %
                         (axis_name, labeled_tensor.axes))

    shape = []
    axes = []
    for axis in labeled_tensor.axes.values():
      if axis.name in shape_map:
        size = shape_map[axis.name]
        shape.append(size)
        # We lose labels for the axes we crop, leaving just the size.
        axes.append((axis.name, size))
      else:
        shape.append(len(axis))
        axes.append(axis)

    crop_op = random_ops.random_crop(labeled_tensor.tensor,
                                     shape,
                                     seed=seed,
                                     name=scope)

    return core.LabeledTensor(crop_op, axes)

def tile(labeled_tensor, multiples, name=None):
  """Constructs a tensor by tiling a given tensor.

  Only axes without tick-labels can be tiled. (Otherwise, axis labels on tiled
  tensors would no longer be unique.)

  See lt.tile.

  Args:
    labeled_tensor: The input tensor.
    multiples: A mapping where the keys are axis names and the values are the
      integer number of times to tile along that axis. Only axes with a multiple
      different than 1 need be included.
    name: Optional op name.

  Returns:
    A tensor with the indicated axes tiled.

  Raises:
    ValueError: If the tiled axes are not axes in the input tensor, or if any
      axes in multiples have tick labels.
  """
  with ops.name_scope(name, 'lt_tile', [labeled_tensor]) as scope:
    labeled_tensor = core.convert_to_labeled_tensor(labeled_tensor)

    if not set(multiples.keys()) <= set(labeled_tensor.axes.keys()):
      raise ValueError('tile axes %r are not contained in the set of axis '
                       'names %r on the input labeled tensor' %
                       (multiples.keys(), labeled_tensor.axes))

    labeled_axes = [
        name for name in multiples
        if labeled_tensor.axes[name].labels is not None
    ]
    if labeled_axes:
      raise ValueError('cannot tile axes with tick labels: %r' % labeled_axes)

    multiples_list = [multiples.get(name, 1) for name in labeled_tensor.axes]
    tile_op = array_ops.tile(labeled_tensor.tensor, multiples_list, name=scope)

    new_axes = [
        axis.name if axis.labels is None else axis
        for axis in labeled_tensor.axes.values()
    ]
    return core.LabeledTensor(tile_op, new_axes)

def verify_tensor_all_finite(labeled_tensor, message, name=None):
  """Asserts a tensor doesn't contain NaNs or Infs.

  See tf.verify_tensor_all_finite.

  Args:
    labeled_tensor: The input tensor.
    message: Message to log on failure.
    name: Optional op name.

  Returns:
    The input tensor.
  """
  with ops.name_scope(name, 'lt_verify_tensor_all_finite',
                      [labeled_tensor]) as scope:
    labeled_tensor = core.convert_to_labeled_tensor(labeled_tensor)
    op = numerics.verify_tensor_all_finite(
        labeled_tensor.tensor, msg=message, name=scope)
    return core.LabeledTensor(op, labeled_tensor.axes)

def map_fn(fn, labeled_tensor, name=None):
  """Map on the list of tensors unpacked from labeled_tensor.

  See tf.map_fn.

  Args:
    fn: The function to apply to each unpacked LabeledTensor.
      It should have type LabeledTensor -> LabeledTensor.
    labeled_tensor: The input tensor.
    name: Optional op name.

  Returns:
    A tensor that packs the results of applying fn to the list of tensors
    unpacked from labeled_tensor.
  """
  with ops.name_scope(name, 'lt_map_fn', [labeled_tensor]) as scope:
    labeled_tensor = core.convert_to_labeled_tensor(labeled_tensor)
    unpack_lts = unpack(labeled_tensor)
    map_lts = [fn(t) for t in unpack_lts]
    return pack(map_lts, list(labeled_tensor.axes.values())[0], name=scope)

def _batch_helper(default_name,
                  batch_fn,
                  batch_size,
                  enqueue_many,
                  labeled_tensors,
                  allow_smaller_final_batch,
                  name=None):
  with ops.name_scope(name, default_name, labeled_tensors) as scope:
    labeled_tensors = [
        core.convert_to_labeled_tensor(lt) for lt in labeled_tensors
    ]

    batch_ops = batch_fn([t.tensor for t in labeled_tensors], scope)
    # TODO(shoyer): Remove this when they sanitize the TF API.
    if not isinstance(batch_ops, list):
      assert isinstance(batch_ops, ops.Tensor)
      batch_ops = [batch_ops]

    if allow_smaller_final_batch:
      batch_size = None

    @tc.returns(core.Axes)
    @tc.accepts(core.Axes)
    def output_axes(axes):
      if enqueue_many:
        if 'batch' not in axes or list(axes.keys()).index('batch') != 0:
          raise ValueError(
              'When enqueue_many is True, input tensors must have an axis '
              'called "batch" as their first dimension, '
              'but axes were %s' % axes)
        culled_axes = axes.remove('batch')
        return core.Axes([('batch', batch_size)] + list(culled_axes.values()))
      else:
        return core.Axes([('batch', batch_size)] + list(axes.values()))

    output_labeled_tensors = []
    for i, tensor in enumerate(batch_ops):
      axes = output_axes(labeled_tensors[i].axes)
      output_labeled_tensors.append(core.LabeledTensor(tensor, axes))

    return output_labeled_tensors

def pack(labeled_tensors, new_axis, axis_position=0, name=None):
  """Pack tensors along a new axis.

  See tf.pack.

  Args:
    labeled_tensors: The input tensors, which must have identical axes.
    new_axis: The name of the new axis, or a tuple containing the name
      and coordinate labels.
    axis_position: Optional integer position at which to insert the new axis.
    name: Optional op name.

  Returns:
    The packed tensors as a single LabeledTensor, with `new_axis` in the given
    `axis_position`.

  Raises:
    ValueError: If fewer than one input tensors is provided, or if the tensors
      don't have identical axes.
  """
  with ops.name_scope(name, 'lt_pack', labeled_tensors) as scope:
    labeled_tensors = [
        core.convert_to_labeled_tensor(lt) for lt in labeled_tensors
    ]

    if len(labeled_tensors) < 1:
      raise ValueError('pack expects at least 1 tensors, but received %s' %
                       labeled_tensors)

    axes_0 = labeled_tensors[0].axes
    for t in labeled_tensors:
      if t.axes != axes_0:
        raise ValueError('Non-identical axes. Expected %s but got %s' %
                         (axes_0, t.axes))

    pack_op = array_ops.stack(
        [t.tensor for t in labeled_tensors], axis=axis_position, name=scope)
    axes = list(axes_0.values())
    axes.insert(axis_position, new_axis)
    return core.LabeledTensor(pack_op, axes)