Function gio_sys::g_menu_model_get_item_attribute_value

pub unsafe extern fn g_menu_model_get_item_attribute_value(model: *mut GMenuModel,
                                                           item_index: c_int,
                                                           attribute: *const c_char,
                                                           expected_type: *const GVariantType)
                                                           -> *mut GVariant