code: def bytes_transform(byte_str, start_idx, stop_idx, fction):
      
      return bytes_replace(byte_str, start_idx, stop_idx, fction(byte_str[start_idx:stop_idx]))
docs: Takes portion of the byte array and passes it to the function for transformation.
      Result is replaced in the byte string, new one is created.
      :param byte_str:
      :param start_idx:
      :param stop_idx:
      :param fction:
      :return: