class_docstr: Test Nodes
code: def test_no_output(self):
      dag = copy.deepcopy(self.dag)
      dag["_output"]["inputs"] = ()
      dag["_output"]["outputs"] = ()
      pipe = RuntimePipeline(dag)
      nums = [1, 2, 3, 4, 5]
      scalar_num = 4
      ret = pipe(scalar_num, nums)
      self.assertEqual(ret.size, 0)
  
file_path: towhee/tests/unittests/runtime/test_nodes.py
imports: import unittest
  import copy
  import threading
  from towhee.runtime.runtime_pipeline import RuntimePipeline
  from towhee.datacollection.data_collection import DataCollection
label_desc: Use image node_id 2 for calling the TestNodesWithFlatMap obj's underlying member method code with example usage: obj.test_no_output() without return types