+/* keycode in specific layer */
+uint8_t keymap_get_keycode(uint8_t layer, uint8_t row, uint8_t col);
+
+/* layer to move during press Fn key */
+uint8_t keymap_fn_layer(uint8_t fn_bits);
+
+/* keycode to send when release Fn key without using */
+uint8_t keymap_fn_keycode(uint8_t fn_bits);