def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def _getProvenanceAfterMetadata(self, item, meta, user):
        resp = self.request(path='/item/%s/metadata' % item['_id'],
                            method='PUT', user=user, body=json.dumps(meta),
                            type='application/json')
        self.assertStatusOk(resp)
        return self._getProvenance(item, user)