如何使用签名gmail api发送电子邮件

import base64
from googleapiclient.discovery import build
from google.oauth2.credentials import Credentials

def send_email(subject, message_text, sender, recipient):
    # 获取存储在本地的用户授权令牌
    credentials = Credentials.from_authorized_user_file('credentials.json')
    # 构建 Gmail API 客户端
    service = build('gmail', 'v1', credentials=credentials)
    
    # 创建电子邮件消息
    message = create_message(subject, message_text, sender, recipient)
    
    # 发送电子邮件
    send_message(service, 'me', message)

def create_message(subject, message_text, sender, recipient):
    message = {
        'subject': subject,
        'text': message_text,
        'to': recipient,
        'from': sender
    }
    message['raw'] = base64.urlsafe_b64encode(message.as_bytes()).decode('utf-8')
    return message

def send_message(service, user_id, message):
    try:
        service.users().messages().send(userId=user_id, body=message).execute()
        print('Message sent successfully.')
    except Exception as e:
        print('An error occurred while sending the message:', str(e))