code: def next(self, x):
      if x < self.threshold:
          return self.children[0]
      return self.children[1]
  
file_path: river/river/tree/test_base.py
imports: from __future__ import annotations
  from river.tree.base import Branch, Leaf
label_desc: Use image node_id 2 for calling the BinaryBranch obj's underlying member method code with example usage: obj.next(x) and returns: self, self