code: def _prune_tree(self):
      if self.ccp_alpha == 0.0:
          return
      n_classes = ivy.atleast_1d(self.n_classes_)
      pruned_tree = Tree(
          self.n_features_in_, n_classes, self.n_outputs_
      )
      self.tree_ = pruned_tree
  
imports: from abc import ABCMeta, abstractmethod
  from ..base import BaseEstimator, ClassifierMixin, MultiOutputMixin
  import copy
  from ._criterion import Gini, Criterion
  from ._splitter import BestSplitter, Splitter
  from ._tree import DepthFirstTreeBuilder, Tree
  import ivy
  import numbers
label_desc: Use image node_id 5 for calling the BaseDecisionTree obj's underlying member method code with example usage: obj._prune_tree() without return types