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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def LocaltimeToUTC(cls, timestamp, timezone, is_dst=False):
 """Converts the timestamp in localtime of the timezone to UTC. Args: timestamp: The timestamp which is an integer containing the number of micro seconds since January 1, 1970, 00:00:00 UTC. timezone: The timezone (pytz.timezone) object. is_dst: A boolean to indicate the timestamp is corrected for daylight savings time (DST) only used for the DST transition period. Returns: The timestamp which is an integer containing the number of micro seconds since January 1, 1970, 00:00:00 UTC or 0 on error. """

    if timezone and timezone != pytz.UTC:
      datetime_object = (
          datetime.datetime(1970, 1, 1, 0, 0, 0, 0, tzinfo=None) +
          datetime.timedelta(microseconds=timestamp))

      # Check if timezone is UTC since utcoffset() does not support is_dst
      # for UTC and will raise.
      datetime_delta = timezone.utcoffset(datetime_object, is_dst=is_dst)
      seconds_delta = int(datetime_delta.total_seconds())
      timestamp -= seconds_delta * definitions.MICROSECONDS_PER_SECOND

    return timestamp