<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def current_revision(self, r_stmts):
 """Pick the most recent revision date. `r_stmts` is a list of 'revision' statements. """

        cur = max([[int(p) for p in r.arg.split("-")] for r in r_stmts])
        return "%4d-%02d-%02d" % tuple(cur)