langchain/memory/chat_message_histories/cosmos_db.py/CosmosDBChatMessageHistory/clear
class CosmosDBChatMessageHistory:    def clear(self) -> None:
        """Clear session memory from this memory and cosmos."""
        self.messages = []
        if self._container:
            self._container.delete_item(
                item=self.session_id, partition_key=self.user_id
            )