protected void removeChild(Node out) {
Validate.isTrue(out.parentNode == this);
int index = out.siblingIndex();
childNodes.remove(index);
reindexChildren();
out.parentNode = null;
}
protected void addChildren(int index, Node... children) {
Validate.noNullElements(children);
for (int i = children.length - 1; i >= 0; i--) {
Node in = children[i];
reparentChild(in);
childNodes.add(index, in);
}
reindexChildren();
}