Leetcode 315 - count of smaller number - study python code, please study the discussion first

Leetcode315_countOfSmallerNumbersAferSelf.py

#https://discuss.leetcode.com/topic/31405/9ms-short-java-bst-solution-get-answer-when-building-bst/2

class TreeNode(object):
    def __init__(self, x, count):
        self.val = x
        self.count = count # the number of points in left bottom
        self.dup = 1
        self.left = None
        self.right = None


class Solution(object):
    def countSmaller(self, nums):
        """
        :type nums: List[int]
        :rtype: List[int]
        """
        length = len(nums)
        self.result = [0] * length
        node = None
        for i in range(length-1,-1,-1):
            node = self.insert(node,nums[i],0,i)
        return self.result
        
    def insert(self,node,value,count,position):
        if node is None:
            node = TreeNode(value,0)
            self.result[position] = count
        elif value == node.val:
            node.dup += 1
            self.result[position] = count + node.count
        elif value > node.val:
            node.right = self.insert(node.right,value,count+node.count+node.dup,position)
        else:
            node.count += 1
            node.left = self.insert(node.left,value,count,position)
        return node