code: def prepare_args(self, args, transform=True):
          
          updated_args = list(args)
          if transform:
              updated_args[-1] = self.transform_value(updated_args[-1])
          if self.key:
              updated_args.insert(-1, self.key)
  
          return updated_args
docs: Prepare args to be used by a sub-index
  
          Parameters
          ----------
          args: list
              The while list of arguments passed to add, check_uniqueness, get_filtered_keys...
          transform: bool
              If ``True``, the last entry in `args`, ie the value, will be transformed.
              Else it will be kept as is.