'Creates a new Volume_type extra spec.
volume_type_id: Id of volume_type.
extra_specs: A dictionary of values to be used as extra_specs.'

def create_volume_type_extra_specs(self, volume_type_id, extra_specs):

    url = ('types/%s/extra_specs' % volume_type_id)
    post_body = json.dumps({'extra_specs': extra_specs})
    (resp, body) = self.post(url, post_body)
    body = json.loads(body)
    self.expected_success(200, resp.status)
    return rest_client.ResponseBody(resp, body)
