code: def getHelper(self, nums, start, end):
      if start > end:
          return None
      mid = (start + end) / 2
      node = TreeNode(nums[mid])
      node.left = self.getHelper(nums, start, mid - 1)
      node.right = self.getHelper(nums, mid + 1, end)
      return node
  
label_desc: Use image node_id 2 for calling the Solution obj's underlying member method code with example usage: obj.getHelper(nums, start, end) and returns: node, None