public static TreeNode fromDom(Node node) {
        String nodeName = node.getNodeName();
        if (nodeName.equalsIgnoreCase("node")) {
            return FeatureNode.fromDom(node);
        } else if (nodeName.equalsIgnoreCase("response")) {
            return ResponseNode.fromDom(node);
        } else {
            throw new UnsupportedOperationException(nodeName);
        }
    }
Returns the number of samples in the training set that matches this node
if this model does not contain this information (i.e if it is not an "ext" model).
searchlib/src/main/java/com/yahoo/searchlib/gbdt/TreeNode.java