Gmail Api Create Draft Reply

I am using the create draft function from googles API documentation:

https://developers.google.com/gmail/api/v1/reference/users/drafts/create

Whenever I send a message I get the following appear in my email message text when I go into gmail:

hello world
Date: Mon, 11 Sep 2017 15:31:19 +0200
Message-Id: <CAKPeGO69TbbigNFrK8T37fYgPzCfZwVf=p0gkvJbZF6duwWsdw@mail.gmail.com>
From: [email protected]

I don’t know why I’m getting all of this text.

What I am trying to do is to create a draft email reply to an existing email but all I seem to get is a new draft with the text above (no to/from/subject fields populated).

Here’s the function I’m using:

import base64
from email.mime.audio import MIMEAudio
from email.mime.base import MIMEBase
from email.mime.image import MIMEImage
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
import mimetypes
import os

def CreateDraft(service, user_id, message_body):
   """Create and insert a draft email. Print the returned draft's message and id.

  Args:
    service: Authorized Gmail API service instance.
    user_id: User's email address. The special value "me"
    can be used to indicate the authenticated user.
    message_body: The body of the email message, including headers.

  Returns:
    Draft object, including draft id and message meta data.
  """
    try:


        draft = service.users().drafts().create(userId=user_id, body=message_body).execute()

        print('Draft id: %snDraft message: %s' % (draft['id'], draft['message']))

        return draft

    except errors.HttpError as error:
        print('An error occurred: %s' % error)
        return None

And here’s how I call it:

 gdraft.CreateDraft(service, user_id='me', message_body=
    {
        'message':
            {'raw': 'aGVsbG8gd29ybGQ=',
             'threadId': '15e5bdc650b1a068',
             'payload': {
                 "mimeType": "multipart/alternative",
                 "headers": [
                     {
                         "name": "In-Reply-To",
                         "value": "<16DCF6644C054E39B1F7F901BDD08EA2@[email protected]>"
                     },
                     {
                         "name": "References",
                         "value": '<16DCF6644C054E39B1F7F901BDD08EA2@[email protected]>'
                     },
                     {
                         "name": "Message-ID",
                         "value": "<16DCF6644C054E39B1F7F901BDD08EA2@[email protected]"
                     },
                     {
                         "name": "Subject",
                         "value": "Re: Software Developer - Hertford"
                     }
                 ]
             }
             }
    })

I have been trying now for four days without a success so I’d really appreciate any help.

UPDATE:

So it seems that I might need to use the createmessage function (based on the comments below); however this doesn’t seem to work in Python3.

I changed:

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

to:

 return {'raw': str(base64.urlsafe_b64encode(message.as_string().encode("utf-8")))}

in an attempt to make it work but I am getting errors:

An error occurred: <HttpError 400 when requesting https://www.googleapis.com/gmail/v1/users/me/drafts?alt=json returned "Missing draft message">