if (child == null) {
if (child == Undefined.instance) {
    public boolean jsFunction_remove(Object child) {        // semantics: if called without arguments, remove self.        // otherwise, remove given subnodes.        if (child == null) {            return node.remove();        } else if (node != null) {            try {                if (child instanceof HopObject) {                    HopObject hobj = (HopObject) child;                    if (hobj.node != null) {                        node.removeNode(hobj.node);                        return true;                    }                }            } catch (Exception x) {                System.err.println("Error in HopObject.remove(): " + x);                x.printStackTrace();            }        }        return false;    }