remove method

bool remove (Object item)
override

Removes value from the set. Returns true if value was in the set. Returns false otherwise. The method has no effect if value value was not in the set.

Implementation 

bool remove(Object item) {
  if (item is! V) return false;

  AvlNode<V> x = _getNode(item as V);
  if (x != null) {
    _removeNode(x);
    return true;
  }
  return false;
}