class_docstr: Custom Action for appending values in an argparse.Namespace.
  
  This action checks that the flag is specified at-most once.
class_docstr_tok: ["Custom","Action","for","appending","values","in","an","argparse.Namespace",".","This","action","checks","that","the","flag","is","specified","at-most","once","."]
code: def __init__(
      self,
      option_strings,
      dest,
      dest_type: type[Any],
      parse_to_dest_type_fn: _PARSEFN,
      **kwargs,
  ):
      super().__init__(option_strings, dest, **kwargs)
      self._dest_type = dest_type
      self._parse_to_dest_type_fn = parse_to_dest_type_fn
  
imports: from __future__ import annotations
  import abc
  import argparse
  import dataclasses
  import enum
  from typing import Any, Callable, Sequence, Tuple, Union
  from google.generativeai.notebook.lib import llmfn_inputs_source
  from google.generativeai.notebook.lib import llmfn_outputs
label_desc: Use image node_id 1 to create a new _MultiValuesAppendAction object from inherited base classes: argparse with example: obj = _MultiValuesAppendAction(option_strings, dest, dest_type, parse_to_dest_type_fn)