function push(i: I): T.Task<void> {
   return R.modifyRef(queue, ys => {
     let xs = ys.slice();
     xs.push(i);
     return xs;
   });
 }

 function remove(key: string): T.Task<void> {
   return modifyRef(subsRef, sbs => {
     let nbs = S.assign({}, sbs);
     delete nbs.cbs[key];
     return nbs;
   });
 }

 return T.co(function* () {
   yield RV.modifyRef(self.sessions, sess => filterSM(sess, s => s.authId !== authId));
   return self.addMockOperation({ authId, tag: 'destroyAllOfAuthId' });
 });

 return T.co(function* () {
   yield RV.modifyRef(self.sessions, sess => SO.remove(sessId, sess) as any);
   return self.addMockOperation({ tag: 'destroy', id: sessId });
 });

 private addMockOperation(op: MockOperation) {
   return RV.modifyRef(this.operations, xs => L.cons(op, xs));
 }