code: def n_prunable_decision_nodes(tree: Tree) -> int:
      """
      The number of prunable decision nodes
      i.e. how many decision nodes have two leaf children
      """
      return len(tree.prunable_decision_nodes)
  
imports: from typing import List
  import numpy
  from ...model import Model
  from ...mutation import TreeMutation, GrowMutation, PruneMutation
  from ...node import LeafNode, TreeNode
  from ...samplers.treemutation import TreeMutationLikelihoodRatio
  from ...sigma import Sigma
  from ...tree import Tree
label_desc: Use image node_id 2 for calling a global function with example usage: n_prunable_decision_nodes(tree) and returns: len