#34;&#34;&#34;
        Removes and interval, do nothing if the interval does not exist.
        &#34;&#34;&#34;
        self._by_start.discard((start, end, data))
        self._by_end.discard((start, end, data))

    def __len__(self):
        &#34;&#34;&#34;
        Returns the number of intervals.
        &#34;&#34;&#34;
        return len(self._by_start)

    def starting_at(self, offset):
        &#34;&#34;&#34;
        Returns an iterable of (start, end, data) tuples where start==offset
        &#34;&#