python - Return a string indicating what type of imbalance exists in a binary search tree -

having added new node avl. kind of rotation need fix it? need write fuction takes binary tree , returns string saying type of imbalaced exist

class node:     """ node in bst. may have left , right subtrees """      def __init__(self, item, left=none, right=none):         self.item = item         self.left = left         self.right = right   class bst:     """ implementation of binary search tree """      def __init__(self, lst=none):         self.root = none         if lst != none:             x in lst:                 self.add(x)      def recurse_add(self, ptr, item):         if ptr == none:             return node(item)         elif item < ptr.item:             ptr.left = self.recurse_add(ptr.left, item)         elif item > ptr.item:             ptr.right = self.recurse_add(ptr.right, item)         return ptr      def add(self, item):         """ add item correct position on tree """         self.root = self.recurse_add(self.root, item)      def r_height(self, ptr):         if ptr == none:             return 0         else:             return 1 + max(self.r_height(ptr.left), self.r_height(ptr.right))      def height(self):         return self.r_height(self.root)