public String getValueString() {
        if( value == null ) {
            return null;
        }
        return Joiner.on( ", " ).join( getValues() );
    }
Whether the tag should appear in the navigation part of the report
<p>
Is either {@code true} or {@code null}
jgiven-core/src/main/java/com/tngtech/jgiven/report/model/Tag.java