def METHOD_NAME(self, usage=None):
    """sets the usage string - if usage not given, uses getusagestring for each option"""
    if usage is None:
        self.usage = (
            "%prog "
            + " ".join(self.getusagestring(option) for option in self.option_list)
            + "\n  "
            + "input directory is searched for PO files with (poconflicts) comments, all entries are written to files in a directory structure for pomerge"
        )
    else:
        super().METHOD_NAME(usage)