code: def _check_blockwise(blockwise):
      if blockwise not in {True, False}:
          raise ValueError(
              "Expected a boolean for 'blockwise "
              "but got {} instead".format(blockwise)
          )
      return blockwise
  
imports: import itertools
  import logging
  import numbers
  import warnings
  import dask
  import dask.array
  import dask.dataframe
  import numpy
  import sklearn.model_selection
  from sklearn.model_selection._split import BaseCrossValidator, _validate_shuffle_split
  from sklearn.utils import check_random_state
  from dask_ml._compat import DASK_2130, DASK_VERSION
  from dask_ml.utils import check_array, check_matching_blocks
  from .._utils import draw_seed
label_desc: Use image node_id 1 for calling a global function with example usage: _check_blockwise(blockwise) and returns: blockwise