method detach

Source

@override
void detach() {
  super.detach();
  if (previousSibling != null) {
    final ContainerParentDataMixin<ChildType> previousSiblingParentData = previousSibling.parentData;
    assert(previousSibling != this);
    assert(previousSiblingParentData.nextSibling == this);
    previousSiblingParentData.nextSibling = nextSibling;
  }
  if (nextSibling != null) {
    final ContainerParentDataMixin<ChildType> nextSiblingParentData = nextSibling.parentData;
    assert(nextSibling != this);
    assert(nextSiblingParentData.previousSibling == this);
    nextSiblingParentData.previousSibling = previousSibling;
  }
  previousSibling = null;
  nextSibling = null;
}