docstr: Abstract method for subclasses.
  
  Returns
  -------
  BaseEstimator
      Should be the *class* (not an instance) to be used for
      transforming blocks of the input.
docstr_tok: ["Abstract","method","for","subclasses",".","Returns","--","--","--","-","BaseEstimator","Should","be","the","*","class","*","(","not","an","instance",")","to","be","used","for","transforming","blocks","of","the","input","."]
code: def _hasher(self) -> sklearn.base.BaseEstimator:
      """
      Abstract method for subclasses.
  
      Returns
      -------
      BaseEstimator
          Should be the *class* (not an instance) to be used for
          transforming blocks of the input.
      """
      raise NotImplementedError
  
imports: import itertools
  import dask
  import dask.array
  import dask.bag
  import dask.dataframe
  import distributed
  import numpy
  import scipy.sparse
  import sklearn.base
  import sklearn.feature_extraction.text
  from dask.delayed import Delayed
  from distributed import get_client, wait
  from sklearn.utils.validation import check_is_fitted
label_desc: Use image node_id 1 for calling the _BaseHasher obj's underlying member method code with example usage: obj._hasher() without return types