code: func (rt *skipListRT) Apply(interval rangetree.Interval, fn func(rangetree.Entry) bool) {
  	rt.apply(rt.top, 0, interval, fn)
  }
docs: // Apply will call the provided function with each entry that exists
  // within the provided range, in order.  Return false at any time to
  // cancel iteration.  Altering the entry in such a way that its location
  // changes will result in undefined behavior.