@Override
    public void setValue(String stringValue) {
        this.value = toBoolean(stringValue);
    }
Sets the value from a string

@param stringValue "true" or "false"
@throws IllegalArgumentException if the given value is not equal to "true" nor "false" (ignoring case)
container-search/src/main/java/com/yahoo/prelude/query/BoolItem.java