code: def test_rbp_empty():
      recs = pd.DataFrame({"item": []})
      truth = pd.DataFrame(
          {"item": [1, 2, 3], "rating": [3.0, 5.0, 4.0]}
      )
      truth = truth.set_index("item")
      assert rbp(recs, truth) == approx(0.0)
  
imports: import logging
  import numpy
  import pandas
  from pytest import approx, mark
  from hypothesis import given
  import hypothesis.strategies
  import hypothesis.extra.numpy
  from lenskit.metrics.topn import rbp, _bulk_rbp
  from lenskit.topn import RecListAnalysis
  from lenskit.util.test import demo_recs
label_desc: Use image node_id 1 for calling a global function with example usage: test_rbp_empty() without return types