使用Python和gmail API，如何发送带有多个附件的消息？

pip install google-api-python-client

import base64
import mimetypes
import os
from email.mime.text import MIMEText
from email.mime.multipart import MIMEMultipart
from email.mime.audio import MIMEAudio
from email.mime.image import MIMEImage
from email.mime.base import MIMEBase
from googleapiclient.discovery import build
from googleapiclient.errors import HttpError
from google.oauth2.credentials import Credentials

# 使用之前设置好的API凭据文件授权访问
credentials = Credentials.from_authorized_user_file('credentials.json', ['https://www.googleapis.com/auth/gmail.compose'])
service = build('gmail', 'v1', credentials=credentials)

def create_message_with_attachments(sender, to, subject, message_text, file_paths):
    message = MIMEMultipart()
    message['to'] = to
    message['from'] = sender
    message['subject'] = subject

    message.attach(MIMEText(message_text, 'plain'))

    for file_path in file_paths:
        content_type, encoding = mimetypes.guess_type(file_path)
        if content_type is None or encoding is not None:
            content_type = 'application/octet-stream'
        main_type, sub_type = content_type.split('/', 1)
        if main_type == 'text':
            with open(file_path, 'r') as file:
                attachment = MIMEText(file.read(), _subtype=sub_type)
        elif main_type == 'image':
            with open(file_path, 'rb') as file:
                attachment = MIMEImage(file.read(), _subtype=sub_type)
        elif main_type == 'audio':
            with open(file_path, 'rb') as file:
                attachment = MIMEAudio(file.read(), _subtype=sub_type)
        else:
            with open(file_path, 'rb') as file:
                attachment = MIMEBase(main_type, sub_type)
                attachment.set_payload(file.read())
            encoders.encode_base64(attachment)
        attachment.add_header('Content-Disposition', 'attachment', filename=os.path.basename(file_path))
        message.attach(attachment)

    return {'raw': base64.urlsafe_b64encode(message.as_bytes()).decode()}

def send_message(service, user_id, message):
    try:
        message = service.users().messages().send(userId=user_id, body=message).execute()
        print('Message sent! Message ID: %s' % message['id'])
        return message
    except HttpError as error:
        print('An error occurred: %s' % error)

sender = 'your_email@gmail.com'
to = 'recipient@example.com'
subject = 'This is the subject'
message_text = 'This is the message body'
file_paths = ['path/to/file1.txt', 'path/to/file2.jpg', 'path/to/file3.mp3']

message = create_message_with_attachments(sender, to, subject, message_text, file_paths)
send_message(service, 'me', message)