def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def call_process(cls, cmd):
        if cls.is_error:
            raise subprocess.CalledProcessError(-1, cmd=cmd, output="Couldn't call xset.")

        if cmd[1:] == ["q"]:
            track = cls.info[cls.index]
            output = "\n".join(track)
            return output