code: public void deleteNode(int treap_node_index, int treap) {
  		touch_();
  		// assert(isValidNode(treap_node_index));
  		if (m_comparator != null)
  			m_comparator.onDeleteImpl_(this, treap_node_index);
  
  		int treap_;
  		if (treap == -1)
  			treap_ = m_defaultTreap;
  		else
  			treap_ = treap;
  
  		if (!m_b_balancing) {
  			unbalancedDelete_(treap_node_index, treap_);
  		} else
  			deleteNode_(treap_node_index, treap_);
  	}
docs: Removes a node from the treap. Throws if doesn't exist.