code: def test_error_when_param_variables_not_permitted(_variables):
      with pytest.raises(ValueError):
          RelativeFeatures(
              variables=_variables,
              reference=["Age", "Name"],
              func=["add", "mul"],
          )
  
imports: import numpy
  import pandas
  import pytest
  from sklearn.pipeline import Pipeline
  from feature_engine.creation import RelativeFeatures
label_desc: Use image node_id 2 for calling a global function with example usage: test_error_when_param_variables_not_permitted(_variables) without return types