code: func (l *PacketIntervalList) MoveAfter(e, mark *PacketIntervalElement) {
  	if e.list != l || e == mark || mark.list != l {
  		return
  	}
  	l.insert(l.remove(e), mark)
  }
docs: // MoveAfter moves element e to its new position after mark.
  // If e or mark is not an element of l, or e == mark, the list is not modified.
  // The element and mark must not be nil.