code: def next(self, x):
      return self.children[self.branch_no(x)]
  
imports: from __future__ import annotations
  import collections
  import math
  from river import base, stats
  from river.tree.base import Branch, Leaf
  from river.utils.math import log_sum_2_exp
label_desc: Use image node_id 3 for calling the MondrianBranch obj's underlying member method code with example usage: obj.next(x) and returns: self