def get(self, key: str, collection: str = DEFAULT_COLLECTION) -> Optional[dict]:
        """
        Get a key-value pair from the Firestore.

        Args:
            key (str): key
            collection (str): collection name

        """
        collection_id = self.firestore_collection(collection)
        result = self._db.collection(collection_id).document(key).get().to_dict()
        if not result:
            return None

        return self.replace_field_name_get(result)

        Get a key-value pair from the Firestore.

        Args:
            key (str): key
            collection (str): collection name

        
llama-index-integrations/storage/kvstore/llama-index-storage-kvstore-firestore/llama_index/storage/kvstore/firestore/base.py