Fetch realms and credentials for the presented request token.

        :param uri: The full URI of the token request.
        :param http_method: A valid HTTP verb, i.e. GET, POST, PUT, HEAD, etc.
        :param body: The request body as a string.
        :param headers: The request headers as a dict.
        :returns: A tuple of 2 elements.
                  1. A list of request realms.
                  2. A dict of credentials which may be useful in creating the
                  authorization form.

def get_realms_and_credentials(self, uri, http_method='GET', body=None,
                                   headers=None):
        """Fetch realms and credentials for the presented request token.

        :param uri: The full URI of the token request.
        :param http_method: A valid HTTP verb, i.e. GET, POST, PUT, HEAD, etc.
        :param body: The request body as a string.
        :param headers: The request headers as a dict.
        :returns: A tuple of 2 elements.
                  1. A list of request realms.
                  2. A dict of credentials which may be useful in creating the
                  authorization form.
        """
        request = self._create_request(uri, http_method=http_method, body=body,
                                       headers=headers)

        if not self.request_validator.verify_request_token(
                request.resource_owner_key, request):
            raise errors.InvalidClientError()

        realms = self.request_validator.get_realms(
            request.resource_owner_key, request)
        return realms, {'resource_owner_key': request.resource_owner_key}