code: def parse_iso_utc(s):
      
      m = rfc3339_datetime_re().match(s)
      if not m:
          raise ValueError( 'Not a valid ISO datetime in UTC: ' + s )
      else:
          fmt = '%Y-%m-%dT%H:%M:%S' + ('.%f' if m.group(7) else '') + 'Z'
          return datetime.datetime.strptime(s, fmt)
docs: Parses an ISO time with a hard-coded Z for zulu-time (UTC) at the end. Other timezones are
      not supported.
  
      :param str s: the ISO-formatted time
  
      :rtype: datetime.datetime
  
      :return: an timezone-naive datetime object
  
      >>> parse_iso_utc('2016-04-27T00:28:04.000Z')
      datetime.datetime(2016, 4, 27, 0, 28, 4)
      >>> parse_iso_utc('2016-04-27T00:28:04Z')
      datetime.datetime(2016, 4, 27, 0, 28, 4)
      >>> parse_iso_utc('2016-04-27T00:28:04X')
      Traceback (most recent call last):
      ...
      ValueError: Not a valid ISO datetime in UTC: 2016-04-27T00:28:04X