1. override
void removeChildRenderObject(RenderObject child)

Remove the given child from renderObject.

The given child is guaranteed to have renderObject as its parent.

Source 

@override
void removeChildRenderObject(RenderObject child) {
  final RenderObjectWithChildMixin<RenderObject> renderObject = this.renderObject;
  assert(renderObject.child == child);
  renderObject.child = null;
  assert(renderObject == this.renderObject);
}