'Return a dictionary to be used as the body of the POST request'

def _post_body(self, user, client, token_type=None):

    body = {'client_id': client.client_id, 'grant_type': 'password', 'username': user.username, 'password': 'test'}
    if token_type:
        body['token_type'] = token_type
    return body
