code: def test_partition_data(self):
      ref_set = set(range(self.n_folds))
      res_set = set(self.cv._partition)
      fold_sizes = np.unique(self.cv._partition, return_counts=True)[1]
  
      self.assertEqual(len(self.data), len(self.cv._partition))
      self.assertEqual(res_set, ref_set)
      np.testing.assert_array_equal(fold_sizes, 2)
  
file_path: cornac/tests/cornac/eval_methods/test_cross_validation.py
imports: import unittest
  import numpy
  from cornac.eval_methods import CrossValidation
  from cornac.data import Reader
label_desc: Use image node_id 2 for calling the TestCrossValidation obj's underlying member method code with example usage: obj.test_partition_data() without return types