code: def add_char(
      inp: List[str], ind: int = 0, char_val: int = 0
  ) -> List[str]:
      list_copy = list(inp)
      list_copy[ind] = chr(122 - char_val) + list_copy[ind]
      return list_copy
  
file_path: captum/tests/robust/test_min_param_perturbation.py
imports: from typing import cast, List
  import torch
  from captum.robust import MinParamPerturbation
  from tests.helpers.basic import assertTensorAlmostEqual, BaseTest
  from tests.helpers.basic_models import BasicModel, BasicModel_MultiLayer
  from torch import Tensor
label_desc: Use image node_id 2 for calling a global function with example usage: add_char(inp, ind, char_val) and returns: list_copy