class_docstr: Mixin to test a bunch of common functionality in models
  deriving from RecommenderBase
code: def test_similar_users(self):
      model = self._get_model()
      model.fit(get_checker_board(50), show_progress=False)
  
      try:
          for userid in range(50):
              ids, _ = model.similar_users(userid, N=10)
              for r in ids:
                  self.assertEqual(r % 2, userid % 2)
      except NotImplementedError:
          pass
  
imports: import os
  import pickle
  import random
  import tempfile
  import numpy
  import pytest
  from numpy.testing import assert_array_equal
  from scipy.sparse import coo_matrix, csr_matrix
  from implicit.evaluation import precision_at_k
  from implicit.nearest_neighbours import ItemItemRecommender
  from implicit.utils import ParameterWarning
label_desc: Use image node_id 6 for calling the RecommenderBaseTestMixin obj's underlying member method code with example usage: obj.test_similar_users() without return types