'Set the specified keys/values of QoS specification.
For a full list of available parameters, please refer to the official
API reference:
http://developer.openstack.org/api-ref/block-storage/v2/#set-keys-in-qos-specification'

def set_qos_key(self, qos_id, **kwargs):

    put_body = json.dumps({'qos_specs': kwargs})
    (resp, body) = self.put(('qos-specs/%s' % qos_id), put_body)
    body = json.loads(body)
    self.expected_success(200, resp.status)
    return rest_client.ResponseBody(resp, body)
