class_docstr: Mixin to test a bunch of common functionality in models
  deriving from RecommenderBase
code: def test_zero_length_row(self):
      # get a matrix where a row/column is 0
      item_users = get_checker_board(50).todense()
      item_users[42] = 0
      item_users[:, 42] = 0
  
      # also set the last row/column to 0 (test out problem reported here
      # https://github.com/benfred/implicit/issues/86#issuecomment-373385686)
      item_users[49] = 0
      item_users[:, 49] = 0
  
      model = self._get_model()
      model.fit(csr_matrix(item_users), show_progress=False)
  
      # item 42 has no users, shouldn't be similar to anything
      for itemid in range(40):
          ids, _ = model.similar_items(itemid, 10)
          self.assertTrue(42 not in 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 12 for calling the RecommenderBaseTestMixin obj's underlying member method code with example usage: obj.test_zero_length_row() without return types