code: def test_classes_attribute(self):
      params = {"ml_task": "binary_classification"}
      model = KNeighborsAlgorithm(params)
      model.fit(self.X, self.y)
  
      try:
          classes = model._classes
      except AttributeError:
          classes = None
  
      self.assertTrue(np.array_equal(np.unique(self.y), classes))
  
imports: import unittest
  import tempfile
  import json
  import numpy
  import pandas
  from numpy.testing import assert_almost_equal
  from sklearn import datasets
  from supervised.algorithms.knn import KNeighborsAlgorithm, KNeighborsRegressorAlgorithm
  from supervised.utils.metric import Metric
  import tempfile
label_desc: Use image node_id 5 for calling the KNeighborsAlgorithmTest obj's underlying member method code with example usage: obj.test_classes_attribute() without return types