<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def timex_ends(self):
 """The list of end positions of ``timexes`` layer elements."""

        if not self.is_tagged(TIMEXES):
            self.tag_timexes()
        return self.ends(TIMEXES)