class_docstr: Option that will be applied in a graph pass.
  
  Each graph pass need to have their own implementation to support the corresponding option.
  Available options are documented in each pass's docstring.
code: def option_val(self):
      return self._option_val
  
file_path: coremltools/coremltools/converters/mil/mil/passes/graph_pass.py
imports: from abc import ABC, abstractmethod
  from typing import Callable, List, Optional, Text, Union
  from coremltools.converters.mil import Operation, Program
label_desc: Use image node_id 4 for calling the PassOption obj's underlying member method code with example usage: obj.option_val() and returns: self