@staticmethod<EOL><INDENT>def metadata_updated_on(item):<DEDENT>
return float(item['<STR_LIT>'])<EOL>
Extracts the update time from a StackExchange item.

        The timestamp is extracted from 'last_activity_date' field.
        This date is a UNIX timestamp but needs to be converted to
        a float value.

        :param item: item generated by the backend

        :returns: a UNIX timestamp