class_docstr: Unit tests for Visualizer.
class_docstr_tok: ["Unit","tests","for","Visualizer","."]
code: def test_dag_visualizer(self):
      p = _get_pipe()
      visualizer.show_graph(p)
  
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 1 for calling the TestVisualizer obj's underlying member method code with example usage: obj.test_dag_visualizer() without return types