public FEELFnResult<String> invoke(@ParameterName("string") String string, @ParameterName("start position") Number start) {
        return invoke(string, start, null);
    }
@Test
    void invokeStartOutOfListBounds() {
        FunctionTestUtil.assertResultError(substringFunction.invoke("test", 10), InvalidParametersEvent.class);
        FunctionTestUtil.assertResultError(substringFunction.invoke("test", 10, null), InvalidParametersEvent.class);
        FunctionTestUtil.assertResultError(substringFunction.invoke("test", -10), InvalidParametersEvent.class);
        FunctionTestUtil.assertResultError(substringFunction.invoke("test", -10, null), InvalidParametersEvent.class);
    }