Gmail API: Python电子邮件字典似乎缺少键

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

def send_email(sender, to, subject, message):
    creds = Credentials.from_authorized_user_file('credentials.json', ['https://www.googleapis.com/auth/gmail.send'])
    service = build('gmail', 'v1', credentials=creds)

    email = {
        'to': to,
        'subject': subject,
        'message': message,
        'from': sender
    }

    try:
        message = create_message(email)
        send_message(service, 'me', message)
        print('Email sent successfully.')
    except HttpError as error:
        print(f'An error occurred: {error}')

def create_message(email):
    message = {
        'raw': base64.urlsafe_b64encode(email.as_bytes()).decode('utf-8')
    }
    return message

def send_message(service, user_id, message):
    service.users().messages().send(userId=user_id, body=message).execute()

# 调用send_email函数发送邮件
send_email('sender@gmail.com', 'recipient@gmail.com', 'Hello', 'This is a test email.')