docs: def add(self, interval: Interval) -> None:
          """
          Adds an interval to the list. If ``self.no_overlap`` is True, as is the
          default, it will merge any overlapping intervals thus created.
          """
          if interval is None:
              return
          if not isinstance(interval, Interval):
              raise TypeError(
                  "Attempt to insert non-Interval into IntervalList")
          self.intervals.append(interval)
          self._tidy()