code: def test_first_obj():
      ftdf = _ftdf()
      ft_clf = FirstObjFtClassifier()
      ft_clf.fit(ftdf[["txt"]], ftdf["lbl"])
  
      assert ft_clf.predict(pd.DataFrame([["woof woof"]]))[0] == 0
      assert ft_clf.predict(pd.DataFrame([["meow meow"]]))[0] == 1
      assert ft_clf.predict(pd.DataFrame([["meow"]]))[0] == 1
      assert ft_clf.predict(pd.DataFrame([["woof lol"]]))[0] == 0
      assert ft_clf.predict(pd.DataFrame([["meow lolz"]]))[0] == 1
  
      with pytest.raises(ValueError):
          assert ft_clf.predict(pd.DataFrame([[5]]))[0] == 1
  
imports: import pytest
  import pandas
  from sklearn.model_selection import cross_val_score
  from skift import FirstColFtClassifier, IdxBasedFtClassifier, ColLblBasedFtClassifier, FirstObjFtClassifier, SeriesFtClassifier
label_desc: Use image node_id 15 for calling a global function with example usage: test_first_obj() without return types