@Override
    protected void onDeserialize(Deserializer buf) {
        super.onDeserialize(buf);
        result = (ResultNode)deserializeOptional(buf);
    }
Constructs an instance of this class with given result.

@param result The result to assign to this.
searchlib/src/main/java/com/yahoo/searchlib/expression/GetDocIdNamespaceSpecificFunctionNode.java