Create a new group dampening

        :param group_id: Group Trigger id attached to dampening
        :param dampening: Dampening definition to be created.
        :type dampening: Dampening
        :return: Group Dampening created

def create_group_dampening(self, group_id, dampening):
        """
        Create a new group dampening

        :param group_id: Group Trigger id attached to dampening
        :param dampening: Dampening definition to be created.
        :type dampening: Dampening
        :return: Group Dampening created
        """
        data = self._serialize_object(dampening)
        url = self._service_url(['triggers', 'groups', group_id, 'dampenings'])
        return Dampening(self._post(url, data))