code: def last_update_time(self, timeformat='unix'):
          
          if self.updated_at is None:
              return None
          return timeformatutils.timeformat(self.updated_at, timeformat)
docs: Returns the UTC time of the last update on this station's metadata
  
          :param timeformat: the format for the time value. May be:
              '*unix*' (default) for UNIX time, '*iso*' for ISO8601-formatted
              string in the format ``YYYY-MM-DD HH:MM:SS+00`` or `date` for
              a ``datetime.datetime`` object
          :type timeformat: str
          :returns: an int or a str or a ``datetime.datetime`` object or None
          :raises: ValueError