docs: def pop(self, index=-1):
          """See list.pop."""
          if not isinstance(index, int):
              if PY2:
                  raise TypeError('an integer is required')
              raise TypeError("'str' object cannot be interpreted as an integer")
          length = len(self)
          if -length <= index < length:
              self._notify_remove_at(index)
          return super(ObservableList, self).pop(index)