def time_conflict(self, schedule):
        """Internal use. Determines when the given time range conflicts with the set of
        excluded time ranges.
        """
        if is_nil(schedule):
            return True
        for timerange in self._excluded_times:
            if timerange.conflicts_with(schedule):
                return False
        return True
Internal use. Determines when the given time range conflicts with the set of
        excluded time ranges.