class SegmentTreeNode(object):    def __init__(self, start, end):        self.start = start        self.end = end        self.sum = 0        self.left = None        self.right = None        class NumArray(object):    def __init__(self, nums):        """        initialize your data structure here.        :type nums: List[int]        """        n = len(nums)        self.root = self.buildTree(nums, 0, n-1)            def update(self, i, val):        """        :type i: int        :type val: int        :rtype: int        """        self.modifyTree(i,val, self.root)            def sumRange(self, i, j):        """        sum of elements nums[i..j], inclusive.        :type i: int        :type j: int        :rtype: int        """        return self.queryTree(i, j, self.root)            def buildTree(self, nums, start, end):        if start > end: return None#not valid        root = SegmentTreeNode(start, end)        if start == end:            root.sum = nums[start]            return root        mid = start + (end - start)/2        root.left = self.buildTree(nums, start, mid)        root.right = self.buildTree(nums, mid+1, end)        root.sum = root.left.sum + root.right.sum        return root            def modifyTree(self, i, val, root):        if not root:            return 0        if root.start==i and root.end == i:             diff = val - root.sum            root.sum = val            return diff        mid = (root.start + root.end)/2        if i > mid:            diff = self.modifyTree(i, val, root.right)        else:            diff = self.modifyTree(i, val, root.left)        root.sum = root.sum + diff        return diff            def queryTree(self, i, j, root):        if not root:            return 0        if root.start == i and root.end == j:            return root.sum        mid = (root.start + root.end)/2        if i > mid:            return self.queryTree(i, j, root.right)        if j <= mid:            return self.queryTree(i, j, root.left)                    return self.queryTree(i, mid, root.left)+self.queryTree(mid+1, j , root.right)                # Your NumArray object will be instantiated and called as such:# numArray = NumArray(nums)# numArray.sumRange(0, 1)# numArray.update(1, 10)# numArray.sumRange(1, 2)