    def test_concat_multi_output(self):
        """
        _input[(a, b, c)]->op1[(a, b)-(d,)]->op3(concat)->_output[(a, d, e)]
                    |------>op2[(c,)-(e,)]----^
        """
        towhee_dag_test = copy.deepcopy(self.dag_dict)
        towhee_dag_test['_input']['next_nodes'] = ['op1', 'op2']
        towhee_dag_test['op1']['next_nodes'] = ['op3']
        towhee_dag_test['op2']['next_nodes'] = ['op3']
        towhee_dag_test['op3'] = {
            'inputs': (),
            'outputs': (),
            'iter_info': {
                'type': 'concat',
                'param': None
            },
            'op_info': {
                'operator': 'concat',
                'type': 'built_in',
                'init_args': None,
                'init_kws': None,
                'tag': None
            },
            'next_nodes': ['_output']
        }
        towhee_dag_test['_output']['inputs'] = ('a', 'd', 'e')
        towhee_dag_test['_output']['outputs'] = ('a', 'd', 'e')

        runtime_pipeline = RuntimePipeline(towhee_dag_test)
        result = runtime_pipeline(2, 2, -10).get()
        self.assertEqual(result[0], 2)
        self.assertEqual(result[1].diff, 0)
        self.assertEqual(result[2].sum, 0)
_input[(a, b, c)]->op1[(a, b)-(d,)]->op3(concat)->_output[(a, d, e)]
|------>op2[(c,)-(e,)]----^
tests/unittests/runtime/test_runtime_pipeline.py