<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def close_files(self):
 """Close all files with an activated disk flag."""

        for name in self:
            if getattr(self, '_%s_diskflag' % name):
                file_ = getattr(self, '_%s_file' % name)
                file_.close()