class_docstr: Unit tests for Visualizer.
class_docstr_tok: ["Unit","tests","for","Visualizer","."]
code: def test_get_tracer(self):
      p = _get_pipe()
      v = Visualizer(
          nodes=p.dag_repr.to_dict().get("nodes"),
          data_queues=[p.preload().data_queues],
          trace_nodes=[i.name for i in p.dag_repr.nodes.values()],
      )
      t = v.tracer[0]
      t["_input"].show()
      self.assertEqual(t["_input"].name, "_input")
      self.assertEqual(t["_input"].op_input, ("a",))
      t["lambda-0"].show()
      self.assertEqual(t["lambda-0"].name, "lambda-0")
      self.assertEqual(t["lambda-0"].op_input, ("a",))
      t["lambda-1"].show()
      self.assertEqual(t["lambda-1"].name, "lambda-1")
      self.assertEqual(t["lambda-1"].op_input, ("b",))
      t["lambda-2"].show()
      self.assertEqual(t["lambda-2"].name, "lambda-2")
      self.assertEqual(t["lambda-2"].op_input, ("b",))
      t["lambda-3"].show()
      self.assertEqual(t["lambda-3"].name, "lambda-3")
      self.assertEqual(t["lambda-3"].op_input, ("b",))
      t["concat-4"].show()
      self.assertEqual(t["concat-4"].name, "concat-4")
      self.assertEqual(t["concat-4"].op_input, ("e", "d", "c"))
      t["_output"].show()
      self.assertEqual(t["_output"].name, "_output")
      self.assertEqual(t["_output"].op_input, ("b", "c", "d", "e"))
      t.show()
  
file_path: towhee/tests/unittests/tools/test_visualizer.py
imports: import unittest
  from towhee import pipe
  from towhee.tools import visualizer
  from towhee.tools.visualizer import Visualizer
  from towhee.runtime.data_queue import DataQueue
label_desc: Use image node_id 3 for calling the TestVisualizer obj's underlying member method code with example usage: obj.test_get_tracer() without return types