code: def key_exists_in_list_or_dict(key, lst_or_dct):
      
      if isinstance(lst_or_dct, dict) and key in lst_or_dct:
          return True
      elif isinstance(lst_or_dct, list):
          min_i, max_i = 0, len(lst_or_dct)
          if min_i <= key < max_i:
              return True
      return False
docs: True if `lst_or_dct[key]` does not raise an Exception