code: def pack_value(index: int) -> bytes:
      
      if PY36:
          return index.to_bytes(1, byteorder="little")
      else:
          return index.to_bytes(2, byteorder="little")
docs: Small helper value to pack an index value into bytecode.
  
      This is used for version compat between 3.5- and 3.6+
  
      :param index: The item to pack.
      :return: The packed item.