class_docstr: test pipeline to triton model
code: def test_failed(self):
      dag_dict = {
          "_input": {
              "inputs": None,
              "outputs": ("a",),
              "iter_info": {"type": "map", "param": None},
              "op_info": {
                  "operator": "NOPNodeOperator",
                  "type": "built_in",
                  "init_args": None,
                  "init_kws": None,
                  "tag": None,
              },
              "next_nodes": ["op1"],
          },
          "op1": {
              "inputs": ("a",),
              "outputs": ("b",),
              "iter_info": {"type": "map", "param": None},
              "op_info": {
                  "operator": "image-decode/cv2",
                  "type": "hub",
                  "init_args": ("x",),
                  "init_kws": {},
                  "tag": "main",
              },
              "config": None,
              "next_nodes": ["_output"],
          },
          "_output": {
              "inputs": ("b",),
              "outputs": ("b",),
              "iter_info": {"type": "map", "param": None},
              "op_info": {
                  "operator": "NOPNodeOperator",
                  "type": "built_in",
                  "init_args": None,
                  "init_kws": None,
                  "tag": None,
              },
              "next_nodes": None,
          },
      }
      config = {"format_priority": ["onnx"]}
      dag_repr = DAGRepr.from_dict(dag_dict)
  
      self.assertFalse(Builder(dag_repr, ".", config).build())
  
file_path: towhee/tests/unittests/serve/triton/test_pipeline_builder.py
imports: import copy
  import unittest
  from pathlib import Path
  from tempfile import TemporaryDirectory
  from towhee.runtime import pipe, ops, AutoConfig
  from towhee.runtime.dag_repr import DAGRepr
  from towhee.serve.triton.constant import PIPELINE_NAME
  from towhee.serve.triton.pipeline_builder import Builder
  from towhee.utils.thirdparty.dill_util import dill
label_desc: Use image node_id 3 for calling the TestPipelineBuilder obj's underlying member method code with example usage: obj.test_failed() without return types