addChild method
Implementation
void addChild(Node child) {
child._parent?._children.remove(child);
child._parent = this;
_children.add(child);
child._markWorldDirty();
}
void addChild(Node child) {
child._parent?._children.remove(child);
child._parent = this;
_children.add(child);
child._markWorldDirty();
}