public FEELFnResult<String> invoke(@ParameterName("from") Object val) {
        if ( val == null ) {
            return FEELFnResult.ofResult( null );
        } else {
            return FEELFnResult.ofResult( TypeUtil.formatValue(val, false) );
        }
    }
@Test
    void invokeMaskNull() {
        FunctionTestUtil.assertResultError(stringFunction.invoke((String) null, null), InvalidParametersEvent.class);
        FunctionTestUtil.assertResultError(stringFunction.invoke((String) null, new Object[]{}),
                                           InvalidParametersEvent.class);
    }