code: private RedBlackTreeNode<Key, Value> deleteMin(RedBlackTreeNode<Key, Value> h) {
  	if (h.getLeft() == null)
  	    return null;
  
  	if (!isRed(h.getLeft()) && !isRed(h.getLeft().getLeft()))
  	    h = moveRedLeft(h);
  
  	h.setLeft(deleteMin(h.getLeft()));
  	return balance(h);
      }
docs: delete the key-value pair with the minimum key rooted at h