<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def flat(self):
 """Return a tuple of alternating kind and id values."""

    flat = []
    for kind, id in self.__pairs:
      flat.append(kind)
      flat.append(id)
    return tuple(flat)