public String toInnerString() {
        return "!" + condition;
    }
A condition which matches if its contained condition doesn't.
NotCondition inverts the term checking but not the label checking.
That is, it means "label:!term", it does not mean "!label:term".

@author bratseth
container-search/src/main/java/com/yahoo/prelude/semantics/rule/NotCondition.java