def METHOD_NAME(event):
    """Convert a GDK Key Event into a Toga key."""
    try:
        key = GDK_KEYS[event.keyval]
        modifiers = set()
        # TODO: Confirm the mapping of Control, Meta and Hyper are correct.
        if event.state & Gdk.ModifierType.LOCK_MASK:
            modifiers.add(Key.CAPSLOCK)
        if event.state & Gdk.ModifierType.SHIFT_MASK:
            modifiers.add(Key.SHIFT)
        if event.state & Gdk.ModifierType.CONTROL_MASK:
            modifiers.add(Key.MOD_1)
        if event.state & Gdk.ModifierType.META_MASK:
            modifiers.add(Key.MOD_2)
        if event.state & Gdk.ModifierType.HYPER_MASK:
            modifiers.add(Key.MOD_3)
        return {"key": key, "modifiers": modifiers}
    except KeyError:
        return None