removedFrom method
Implementation
void removedFrom(ContainerNode insertionPoint) {
  assert(insertionPoint.isConnected || isContainerNode());
  if (insertionPoint.isConnected) {
    _isConnected = false;
  }
}void removedFrom(ContainerNode insertionPoint) {
  assert(insertionPoint.isConnected || isContainerNode());
  if (insertionPoint.isConnected) {
    _isConnected = false;
  }
}