.info(&#34;DEBUG: set laststart to None&#34;)
        for intvl in self._by_start.irange_key():
            # logger.info(&#34;DEBUG: checking interval {}&#34;.format(intvl))
            if laststart is None:
                laststart = intvl[0]
                # logger.info(&#34;DEBUG: setting laststart to {} and yielding {}&#34;.format(intvl[0], intvl))
                yield intvl
            elif intvl[0] == laststart:
                # logger.info(&#34;DEBUG: yielding {}&#34;.format(intvl))
            