def get_loaded_field_names(self):
        # We cache this because we call this function multiple times
        # (compiler.fill_related_selections, query.iterator)
        try:
            return self._loaded_field_names_cache
        except AttributeError:
            collection = {}
            self.deferred_to_data(collection, self.get_loaded_field_names_cb)
            self._loaded_field_names_cache = collection
            return collection
If any fields are marked to be deferred, returns a dictionary mapping
dataset/ETHPy150Open django/django/django/db/models/sql/query.py/Query.get_loaded_field_names