docs: def gaps(self) -> "IntervalList":
          """
          Returns all the gaps between intervals, as an :class:`IntervalList`.
          """
          if len(self.intervals) < 2:
              return IntervalList(None)
          gaps = []
          for i in range(len(self.intervals) - 1):
              gap = Interval(
                  self.intervals[i].end,
                  self.intervals[i + 1].start
              )
              gaps.append(gap)
          return IntervalList(gaps)