class_docstr: Unit test for data visualizers.
code: def test_false_node(self):
      p = _get_pipe()
      q = _get_node_queue()
      pv = PipeVisualizer(p.dag_repr.to_dict().get("nodes"), q)
      with self.assertRaises(KeyError):
          _ = pv["test"]
  
file_path: towhee/tests/unittests/tools/test_data_visualizer.py
imports: import unittest
  from towhee import pipe
  from towhee.tools.data_visualizer import PipeVisualizer
  from towhee.datacollection import DataCollection
  from towhee.runtime.data_queue import DataQueue, ColumnType
label_desc: Use image node_id 2 for calling the TestDataVisualizer obj's underlying member method code with example usage: obj.test_false_node() without return types