def only(self, *fields):
        self._loaded_fields = []
        for field in fields:
            if '.' in field:
                raise InvalidQueryError('Subfields cannot be used as '
                                        'arguments to QuerySet.only')
            # Translate field name
            field = QuerySet._lookup_field(self._document, field)[-1].db_field
            self._loaded_fields.append(field)

        # _cls is needed for polymorphism
        if self._document._meta.get('allow_inheritance'):
            self._loaded_fields += ['_cls']
        return self
Return True if this Column references the given column via foreign
dataset/ETHPy150Open aparo/django-elasticsearch/django_elasticsearch/manager.py/QuerySet.only--crossover with--dataset/ETHPy150Open RoseOu/flasky/venv/lib/python2.7/site-packages/sqlalchemy/sql/schema.py/Column.references