def __call__(self, **kwargs):
        """
        kwargs: keys should be in the mmap name set

        Returns a (mask, values) tuple.
        """
        mask = 0
        values = []
        for m, s in self.mmap:
            if s in kwargs:
                val = kwargs.get(s)
                if val is not None:
                    mask |= m
                    values.append(getattr(val, "_maskvalue", val))
                del kwargs[s]
        if kwargs:
            raise ValueError(f"Unknown mask names: {list(kwargs.keys())}")
        return mask, values

        kwargs: keys should be in the mmap name set

        Returns a (mask, values) tuple.
        
libqtile/backend/x11/xcbq.py