def FilterRange(self, start_time=None, stop_time=None):
    """Filter the series to lie between start_time and stop_time.

    Removes all values of the series which are outside of some time range.

    Args:
      start_time: If set, timestamps before start_time will be dropped.
      stop_time: If set, timestamps at or past stop_time will be dropped.
    """

    start_time = self._NormalizeTime(start_time)
    stop_time = self._NormalizeTime(stop_time)
    self.data = [
        p for p in self.data
        if (start_time is None or p[1] >= start_time) and
        (stop_time is None or p[1] < stop_time)
    ]