code: def test_get_feature_names_out_raises_error_when_wrong_param(
      _input_features, df_vartypes
  ):
      transformer = RelativeFeatures(
          variables=["Age", "Marks"],
          reference=["Age", "Marks"],
          func=["add", "sub"],
      )
      transformer.fit(df_vartypes)
  
      with pytest.raises(ValueError):
          transformer.get_feature_names_out(
              input_features=_input_features
          )
  
imports: import numpy
  import pandas
  import pytest
  from sklearn.pipeline import Pipeline
  from feature_engine.creation import RelativeFeatures
label_desc: Use image node_id 18 for calling a global function with example usage: test_get_feature_names_out_raises_error_when_wrong_param(_input_features, df_vartypes) without return types