List all subdocuments of the current collection.

        Args:
            page_size (Optional[int]]): The maximum number of documents
            in each page of results from this request. Non-positive values
            are ignored. Defaults to a sensible value set by the API.

        Returns:
            Sequence[~.firestore_v1beta1.collection.DocumentReference]:
                iterator of subdocuments of the current collection. If the
                collection does not exist at the time of `snapshot`, the
                iterator will be empty

def list_documents(self, page_size=None):
        """List all subdocuments of the current collection.

        Args:
            page_size (Optional[int]]): The maximum number of documents
            in each page of results from this request. Non-positive values
            are ignored. Defaults to a sensible value set by the API.

        Returns:
            Sequence[~.firestore_v1beta1.collection.DocumentReference]:
                iterator of subdocuments of the current collection. If the
                collection does not exist at the time of `snapshot`, the
                iterator will be empty
        """
        parent, _ = self._parent_info()

        iterator = self._client._firestore_api.list_documents(
            parent,
            self.id,
            page_size=page_size,
            show_missing=True,
            metadata=self._client._rpc_metadata,
        )
        iterator.collection = self
        iterator.item_to_value = _item_to_document_ref
        return iterator