protected String buildConstraintsString() {
        String operatorString = operator != null ? operator.getCustomOperator() : "";
        return kiePMMLOperatorValues.stream().map(KiePMMLOperatorValue::getConstraintsAsString).collect(Collectors.joining(" " + operatorString + " "));
    }
@Test
    void buildConstraintsString() {
        KiePMMLFieldOperatorValue kiePMMLFieldOperatorValue = getKiePMMLFieldOperatorValueWithName();
        String expected = "value < 35 surrogate value > 85";
        String retrieved = kiePMMLFieldOperatorValue.buildConstraintsString();
        assertThat(retrieved).isEqualTo(expected);
        kiePMMLFieldOperatorValue = getKiePMMLFieldOperatorValueWithoutName();
        expected = "value < 35 surrogate value > 85";
        retrieved = kiePMMLFieldOperatorValue.buildConstraintsString();
        assertThat(retrieved).isEqualTo(expected);
    }