public static TestAndSetCondition fromConditionString(Optional<String> conditionString) {
        return conditionString
                .map(TestAndSetCondition::new)
                .orElse(TestAndSetCondition.NOT_PRESENT_CONDITION);
    }
Maps and optional test and set condition string to a TestAndSetCondition.
If the condition string is not present, a "not present" condition is returned
@param conditionString test and set condition string (document selection)
@return a TestAndSetCondition representing the condition string or a "not present" condition
document/src/main/java/com/yahoo/document/TestAndSetCondition.java