'Prepare the access token request body.
The client makes a request to the token endpoint by adding the
following parameters using the "application/x-www-form-urlencoded"
format in the HTTP request entity-body:
grant_type
REQUIRED.  Value MUST be set to "authorization_code".
code
REQUIRED.  The authorization code received from the
authorization server.
redirect_uri
REQUIRED, if the "redirect_uri" parameter was included in the
authorization request as described in Section 4.1.1, and their
values MUST be identical.
.. _`Section 4.1.1`: http://tools.ietf.org/html/draft-ietf-oauth-v2-28#section-4.1.1'

def prepare_request_body(self, code, body=u'', redirect_uri=None, **kwargs):

    redirect_uri = (redirect_uri or self.default_redirect_uri)
    code = (code or self.code)
    return prepare_token_request(u'authorization_code', code=code, body=body, redirect_uri=redirect_uri, **kwargs)
