code: def add_child(self, child_node):  # type: (Node) -> None
      assert child_node not in self.children
      self.children.append(child_node)
      if self not in child_node.parents:
          child_node.parents.append(self)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from __future__ import unicode_literals
  from onnx import numpy_helper, ValueInfoProto, AttributeProto, GraphProto, NodeProto, TensorProto, TensorShapeProto
  from typing import Any, Text, Iterable, List, Dict, Sequence, Optional, Tuple, Union
  from typing_extensions import Protocol
  import numpy
label_desc: Use image node_id 3 for calling the Node obj's underlying member method code with example usage: obj.add_child(child_node) without return types