def assign_to(self, user_id):
    return self._api.call(PUT('/projects/{0.project_id}/merge_requests/{0.iid}'.format(self), {'assignee_id': user_id}))
def assign_to(self, user_id):
    return self._api.call(PUT('/projects/{0.project_id}/merge_requests/{0.iid}'.format(self), {'assignee_id': user_id}))