This method returns a GraphQLQuery (from cache if present)

def document_from_string(self, schema, request_string):
        # type: (GraphQLSchema, str) -> GraphQLDocument
        """This method returns a GraphQLQuery (from cache if present)"""
        key = self.get_key_for_schema_and_document_string(schema, request_string)
        if key not in self.cache_map:
            # We return from the fallback
            self.cache_map[key] = self.fallback_backend.document_from_string(
                schema, request_string
            )
            # We ensure the main backend response is in the queue
            self.get_worker().queue(self.queue_backend, key, schema, request_string)

        return self.cache_map[key]