class_docstr: Unit test for Visualizer.
class_docstr_tok: ["Unit","test","for","Visualizer","."]
code: def test_show(self):
      v = GraphVisualizer(self.p.dag_repr)
      v.show()
  
      data = v._get_data()
      self.assertTrue(len(data), 7)
  
imports: import unittest
  from towhee import pipe, ops
  from towhee.tools.graph_visualizer import GraphVisualizer
label_desc: Use image node_id 1 for calling the TestVisualizer obj's underlying member method code with example usage: obj.test_show() without return types