Get history/version information for this datastream and
        return as an instance of
        :class:`~eulfedora.xml.DatastreamHistory`.

def history(self):
        '''Get history/version information for this datastream and
        return as an instance of
        :class:`~eulfedora.xml.DatastreamHistory`.'''
        r = self.obj.api.getDatastreamHistory(self.obj.pid, self.id, format='xml')
        return parse_xml_object(DatastreamHistory, r.content, r.url)