code: def test_learn_many_not_fit(batch_model):
      """Ensure that Naives Bayes models return an empty DataFrame when not yet fitted. Also check
      that the predict_proba_many method keeps the index.
      """
      assert batch_model.predict_proba_many(
          pd.Series(["new", "unseen"], index=["river", "rocks"])
      ).equals(pd.DataFrame(index=["river", "rocks"]))
  
      assert batch_model.predict_many(
          pd.Series(["new", "unseen"], index=["river", "rocks"])
      ).equals(pd.DataFrame(index=["river", "rocks"]))
  
file_path: river/river/naive_bayes/test_naive_bayes.py
imports: from __future__ import annotations
  import pandas
  import pytest
  from sklearn import naive_bayes
  from river import compose, feature_extraction, naive_bayes
label_desc: Use image node_id 9 for calling a global function with example usage: test_learn_many_not_fit(batch_model) without return types