class_docstr: Unit tests for Visualizer.
class_docstr_tok: ["Unit","tests","for","Visualizer","."]
code: def test_show_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()],
      )
      v.tracer.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 2 for calling the TestVisualizer obj's underlying member method code with example usage: obj.test_show_tracer() without return types