langchain/tools/gmail/send_message.py/GmailSendMessage/_run
class GmailSendMessage:    def _run(
        self,
        message: str,
        to: List[str],
        subject: str,
        cc: Optional[List[str]] = None,
        bcc: Optional[List[str]] = None,
        run_manager: Optional[CallbackManagerForToolRun] = None,
    ) -> str:
        """Run the tool."""
        try:
            create_message = self._prepare_message(message, to, subject, cc=cc, bcc=bcc)
            send_message = (
                self.api_resource.users()
                .messages()
                .send(userId="me", body=create_message)
            )
            sent_message = send_message.execute()
            return f'Message sent. Message Id: {sent_message["id"]}'
        except Exception as error:
            raise Exception(f"An error occurred: {error}")