code: def test_shrinkage_field(u1_ml100k, pkf):
      """Ensure the shrinkage field is taken into account."""
  
      sim_options = {"name": "pearson_baseline", "shrinkage": 0}
      bsl_options = {"n_epochs": 1}
      algo = KNNBasic(sim_options=sim_options)
      rmse_shrinkage_0 = cross_validate(algo, u1_ml100k, ["rmse"], pkf)[
          "test_rmse"
      ]
  
      sim_options = {"name": "pearson_baseline", "shrinkage": 100}
      bsl_options = {"n_epochs": 1}
      algo = KNNBasic(sim_options=sim_options, bsl_options=bsl_options)
      rmse_shrinkage_100 = cross_validate(
          algo, u1_ml100k, ["rmse"], pkf
      )["test_rmse"]
  
      assert rmse_shrinkage_0 != rmse_shrinkage_100
  
imports: from itertools import combinations
  import pytest
  from surprise import KNNBaseline, KNNBasic, KNNWithMeans
  from surprise.model_selection import cross_validate
label_desc: Use image node_id 3 for calling a global function with example usage: test_shrinkage_field(u1_ml100k, pkf) without return types