code: def is_old_sklearn(fitted):
      # to be compatible with old sklearn (reference version 0.22.1)
      return hasattr(fitted, "_necessary_X_")
  
file_path: h2o-3/h2o-py/tests/testdir_algos/isotonic/pyunit_isotonic.py
imports: import sys
  from tests import pyunit_utils
  import numpy
  import pandas
  from pandas.testing import assert_frame_equal
  from sklearn.datasets import make_regression
  from sklearn.isotonic import IsotonicRegression
  import h2o
  from h2o import H2OFrame
  from h2o.estimators.isotonicregression import H2OIsotonicRegressionEstimator
label_desc: Use image node_id 2 for calling a global function with example usage: is_old_sklearn(fitted) and returns: hasattr