class_docstr: Visitor to produce a human readable string for a graph.
code: def validate_value(self, value: pydot.Node):
      assert isinstance(value, pydot.Node)
  
imports: import abc
  import collections
  import dataclasses
  from typing import Any, Collection, Dict, List, Optional, Tuple
  import pydot
label_desc: Use image node_id 4 for calling the _PrintGraphVisitor obj's underlying member method code with example usage: obj.validate_value(value) without return types