code: def _shrink(self, reg_param):
      for tree in self.trees_:
          tree.shrink(reg_param)
  
imports: from copy import deepcopy
  from typing import List
  import numpy
  from sklearn import datasets
  from sklearn.base import BaseEstimator
  from sklearn.metrics import r2_score
  from sklearn.model_selection import cross_val_score
  from sklearn.model_selection import train_test_split
  from sklearn.tree import DecisionTreeRegressor
  from imodels.util import checks
label_desc: Use image node_id 5 for calling the HSFIGS obj's underlying member method code with example usage: obj._shrink(reg_param) without return types