Function xkbcommon_sys::xkb_keymap_num_levels_for_key

pub unsafe extern "C" fn xkb_keymap_num_levels_for_key(
    keymap: *mut xkb_keymap, 
    key: xkb_keycode_t, 
    layout: xkb_layout_index_t
) -> xkb_level_index_t