<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def set_mtime(self, name, mtime, size):
 """Set modification time on file."""

        self.check_write(name)
        os.utime(os.path.join(self.cur_dir, name), (-1, mtime))