code: def build_tree(self):
      for i in range(self.size - 1, 0, -1):
          self.tree[i] = self.fn(self.tree[i * 2], self.tree[i * 2 + 1])
  
label_desc: Use image node_id 2 for calling the SegmentTree obj's underlying member method code with example usage: obj.build_tree() without return types