code: def __reduce__(self):
      return (
          CVCache,
          (
              self.splits,
              self.pairwise,
              self.cache is not None,
              self.num_train_samples,
          ),
      )
  
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 2 for calling the CVCache obj's underlying member method code with example usage: obj.__reduce__() and returns: CVCache,  self,  self,  unknown,  self