class_docstr: Helper class to parse boolean flag that optionally accepts truth value.
code: def __call__(self, parser, namespace, values, option_string=None):
      if values is None:
          # Handling `--boolean_flag`.
          # Without additional arguments, it implies true.
          flag_value = True
      elif values.lower() == "true":
          # Handling `--boolean_flag=true`.
          # (Case insensitive after the equal sign)
          flag_value = True
      elif values.lower() == "false":
          # Handling `--boolean_flag=false`.
          # (Case insensitive after the equal sign)
          flag_value = False
      else:
          raise ValueError(
              "Invalid argument to --{}. Must use flag alone,"
              " or specify true/false.".format(self.dest)
          )
      setattr(namespace, self.dest, flag_value)
  
imports: import argparse
  import os
  import sys
  import warnings
  from absl import app
  import tensorflow
  from tensorflow.lite.python import lite
  from tensorflow.lite.python.convert import register_custom_opdefs
  from tensorflow.lite.toco import toco_flags_pb2
  from tensorflow.lite.toco.logging import gen_html
  from tensorflow.python import tf2
  from tensorflow.python.framework import dtypes
  from tensorflow.python.platform import gfile
  from tensorflow.python.util import keras_deps
label_desc: Use image node_id 2 for calling the _ParseBooleanFlag obj's underlying member method code with example usage: obj.__call__(parser, namespace, values, option_string) without return types