class_docstr: Mixin to test a bunch of common functionality in models
  deriving from RecommenderBase
code: def test_pickle(self):
      user_items = get_checker_board(50)
      model = self._get_model()
      model.fit(user_items, show_progress=False)
  
      pickled = pickle.dumps(model)
      reloaded = pickle.loads(pickled)
  
      # make sure we can call methods on the reloaded index, and get the same results back
      # (https://github.com/benfred/implicit/issues/631)
      ids, _ = model.recommend(0, user_items[0])
      reloaded_ids, _ = reloaded.recommend(0, user_items[0])
      assert_array_equal(ids, reloaded_ids)
  
      ids, _ = model.similar_items(0)
      reloaded_ids, _ = reloaded.similar_items(0)
      assert_array_equal(ids, reloaded_ids)
  
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 18 for calling the RecommenderBaseTestMixin obj's underlying member method code with example usage: obj.test_pickle() without return types