code: def extract_param(self, key, x, n):
      if self.cache is not None and (n, key) in self.cache:
          return self.cache[n, key]
  
      out = _index_param_value(
          self.num_train_samples, x, self.splits[n][0]
      )
  
      if self.cache is not None:
          self.cache[n, key] = out
      return out
  
imports: from __future__ import absolute_import, division, print_function
  import warnings
  from collections import defaultdict
  from threading import Lock
  from timeit import default_timer
  import numpy
  import packaging.version
  from dask.base import normalize_token
  from scipy import sparse
  from scipy.stats import rankdata
  from sklearn.exceptions import FitFailedWarning
  from sklearn.pipeline import FeatureUnion, Pipeline
  from sklearn.utils.validation import check_consistent_length
  from toolz import pluck
  from .._compat import Mapping
  from .utils import _index_param_value, _num_samples, _safe_indexing, copy_estimator
label_desc: Use image node_id 5 for calling the CVCache obj's underlying member method code with example usage: obj.extract_param(key, x, n) and returns: out, self