code: def _add(self, other):
          
          if len([interval for interval in self if other in interval]) > 0:  # if other is already represented
              return
          # remove any intervals which are fully represented by the interval we are adding
          to_remove = [interval for interval in self if interval in other]
          self._data.difference_update(to_remove)
          self._data.add(other)
docs: Add a interval to the underlying IntervalSet data store. This does not perform any tests as we assume that
          any requirements have already been checked and that this function is being called by an internal function such
          as union(), intersection() or add().
          :param other: An Interval to add to this one