I want to use gmail API in google collateral, but there is an error during authentication.

 pip install --upgrade google-api-python-client google-auth-httplib2google-auth-oauthlib

from__future_import print_function
importos.path
from googleapiclient.discovery import build
from google_auth_oauthlib.flow import InstalledAppFlow
from google.auth.transport.requests import Request
from google.oauth2.credentials import Credentials

from email.mime.text import MIMEText
import base64


# If modifying these scopes, delete the file token.json.
SCOPES= ['https://www.googleapis.com/auth/gmail.send']

create_message(sender, to, subject, message_text):
    message = MIMEText(message_text)
    message ['to'] = to
    message ['from'] = sender
    message ['subject'] = subject
    return {'raw':base64.urlsafe_b64encode(message.as_string().encode()) .decode}

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

defmain():
    "Shows basic usage of the Gmail API.
    Lists the user's Gmail labels.
    """
    credits = None
    # The file token.json stores the user's access and refresh tokens, and is
    # created automatically when the authorization flow complements for the first
    # time
    ifos.path.exists('token.json'):
        credits = Credentials.from_authorized_user_file('token.json', SCOPES)
    # If there are no (valid) credentials available, let the user log in.
    if not cred or not cred.valid:
        if credits and credits.expired and credits.refresh_token:
            credits.refresh (Request())
        else:
            flow = InstalledAppFlow.from_client_secrets_file(
                '/content/drive/MyDrive/****/****.json', SCOPES)
            credits=flow.run_local_server(port=0)
        # Save the credentials for the next run
        with open('token.json', 'w') as token:
            token.write(creds.to_json())

    service=build('gmail', 'v1', credentials=creds)

    sender='[email protected]'
    to='[email protected]'
    subject = 'Test Mail'
    message_text='This is a test email from the Gmail API.'

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

main()