@Override
    public RelevanceNode clone() {
        RelevanceNode obj = (RelevanceNode)super.clone();
        obj.relevance = (FloatResultNode)relevance.clone();
        return obj;
    }
This abstract expression node represents a function to execute.

@author baldersheim
@author Simon Thoresen Hult
searchlib/src/main/java/com/yahoo/searchlib/expression/RelevanceNode.java