code: def test_sanity_checks(u1_ml100k, pkf, algo, expected_rmse):
      """Basic sanity checks for all algorithms: check that RMSE stays the same."""
  
      trainset, testset = next(pkf.split(u1_ml100k))
      algo.fit(trainset)
      predictions = algo.test(testset)
      assert not all(
          pred.details["was_impossible"] for pred in predictions
      )
      assert accuracy.rmse(predictions, verbose=False) == expected_rmse
  
imports: import os
  import pytest
  from surprise import accuracy, BaselineOnly, CoClustering, Dataset, KNNBaseline, KNNBasic, KNNWithMeans, KNNWithZScore, NMF, NormalPredictor, Reader, SlopeOne, SVD, SVDpp
  from surprise.model_selection import train_test_split
label_desc: Use image node_id 4 for calling a global function with example usage: test_sanity_checks(u1_ml100k, pkf, algo, expected_rmse) without return types