code: def to_epoch(t_str):
      
      try:
          t = float(t_str)
          return t
      except ValueError:
          for format in constants.TIMESTAMP_STR_FORMATS:
              try:
                  t = datetime.datetime.strptime(t_str, format)
                  return float(time.mktime(t.utctimetuple()) * 1000.0 + t.microsecond / 1000.0)
              except ValueError:
                  pass
      raise exceptions.InvalidDataFormat
docs: Covert a timestamp string to an epoch number.
      :param str t_str: a timestamp string.
      :return int: epoch number of the timestamp.