code: def test_mrr_norel_zero():
      "no relevant items -> zero"
      rr = _test_rr([1, 2, 3], [4, 5])
      assert rr == approx(0)
  
file_path: lkpy/tests/test_topn_mrr.py
imports: import numpy
  import pandas
  from pytest import approx, mark
  from lenskit.topn import RecListAnalysis, recip_rank
  from lenskit.util.test import ml_test, demo_recs
  from lenskit.algorithms.basic import Popular
  from lenskit.batch import recommend
  from lenskit.crossfold import simple_test_pair
label_desc: Use image node_id 3 for calling a global function with example usage: test_mrr_norel_zero() without return types