class_docstr: Unit test for Config.
code: def test_config_user_config(self):
      pipe = (
          towhee.pipe.input("a")
          .map("a", "b", add, {"name": "add_1"})
          .map("b", "c", add, {"name": "add_1"})
          .map("a", "d", add, {"name": "add_2"})
          .output("a", "b", "c", "d")
      )
      graph = pipe.preload()
      self.assertEqual(
          [v.name for _, v in graph._nodes.items()],
          ["_input", "add_1", "add_1", "add_2", "_output"],
      )
      self.assertEqual(pipe(1).get(), [1, 2, 3, 2])
  
imports: import unittest
  import towhee
  from towhee.runtime import ops, register
label_desc: Use image node_id 11 for calling the TestConfig obj's underlying member method code with example usage: obj.test_config_user_config() without return types