def test_walk_stack(self):
     def deeper():
         return list(traceback.walk_stack(None))
     s1 = list(traceback.walk_stack(None))
     s2 = deeper()
     self.assertEqual(len(s2) - len(s1), 1)
     self.assertEqual(s2[1:], s1)

def extract_stack(f=None, limit=None):
    """Replacement for traceback.extract_stack() that only does the
    necessary work for asyncio debug mode.
    """
    if f is None:
        f = sys._getframe().f_back
    if limit is None:
        # Limit the amount of work to a reasonable amount, as extract_stack()
        # can be called for each coroutine and future in debug mode.
        limit = constants.DEBUG_STACK_DEPTH
    stack = traceback.StackSummary.extract(traceback.walk_stack(f),
                                           limit=limit,
                                           lookup_lines=False)
    stack.reverse()
    return stack

def f():
    summary = traceback.StackSummary.extract(
        traceback.walk_stack(None)
    )
    print(''.join(summary.format()))

 def some_inner(k, v):
     a = 1
     b = 2
     return traceback.StackSummary.extract(
         traceback.walk_stack(None), capture_locals=True, limit=1)

 def test_extract_stack_limit(self):
     s = traceback.StackSummary.extract(traceback.walk_stack(None), limit=5)
     self.assertEqual(len(s), 5)

 def test_extract_stack(self):
     s = traceback.StackSummary.extract(traceback.walk_stack(None))
     self.assertIsInstance(s, traceback.StackSummary)

 def test_walk_stack(self):
     s = list(traceback.walk_stack(None))
     self.assertGreater(len(s), 10)

def f():
    summary = traceback.StackSummary.extract(
        traceback.walk_stack(None)
    )
    for fs in summary:
        print(template.format(fs=fs))

 def deeper():
     return list(traceback.walk_stack(None))