def get_document_summary(self, doc_id: str) -> str:
        """
        Get document summary by doc id.

        Args:
            doc_id (str): A document id.

        """
        if doc_id not in self._index_struct.doc_id_to_summary_id:
            raise ValueError(f"doc_id {doc_id} not in index")
        summary_id = self._index_struct.doc_id_to_summary_id[doc_id]
        return self.docstore.get_node(summary_id).get_content()

        Get document summary by doc id.

        Args:
            doc_id (str): A document id.

        
llama-index-core/llama_index/core/indices/document_summary/base.py