'Add the client credentials to the request body.
The client makes a request to the token endpoint by adding the
following parameters using the "application/x-www-form-urlencoded"
format per `Appendix B`_ in the HTTP request entity-body:
:param scope:   The scope of the access request as described by
`Section 3.3`_.
:param kwargs:  Extra credentials to include in the token request.
The client MUST authenticate with the authorization server as
described in `Section 3.2.1`_.
The prepared body will include all provided credentials as well as
the ``grant_type`` parameter set to ``client_credentials``::
>>> from oauthlib.oauth2 import BackendApplicationClient
>>> client = BackendApplicationClient(\'your_id\')
>>> client.prepare_request_body(scope=[\'hello\', \'world\'])
\'grant_type=client_credentials&scope=hello+world\'
.. _`Appendix B`: http://tools.ietf.org/html/rfc6749#appendix-B
.. _`Section 3.3`: http://tools.ietf.org/html/rfc6749#section-3.3
.. _`Section 3.2.1`: http://tools.ietf.org/html/rfc6749#section-3.2.1'

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

    return prepare_token_request(u'client_credentials', body=body, scope=scope, **kwargs)
