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 invokeDurationMinutes() {
        FunctionTestUtil.assertResult(stringFunction.invoke(Duration.ofMinutes(9)), "PT9M");
        FunctionTestUtil.assertResult(stringFunction.invoke(Duration.ofMinutes(200)), "PT3H20M");
        FunctionTestUtil.assertResult(stringFunction.invoke(Duration.ofMinutes(5000)), "P3DT11H20M");
        FunctionTestUtil.assertResult(stringFunction.invoke(Duration.ofMinutes(-5000)), "-P3DT11H20M");
    }