code: def test_non_numerical_error():
      df = pd.DataFrame({"y": ["a"], "x": ["featX"]})
      with pytest.raises(TypeError) as type_error:
          DFtoVW(
              df=df, label=SimpleLabel(label="y"), features=Feature("x")
          )
      expected = "In argument 'label' of 'SimpleLabel', column 'y' should be either of the following type(s): 'int', 'float'."
      assert expected == str(type_error.value)
  
imports: import pytest
  import pandas
  from vowpalwabbit.dftovw import ContextualbanditLabel, DFtoVW, Feature, MulticlassLabel, MultiLabel, Namespace, SimpleLabel
label_desc: Use image node_id 18 for calling a global function with example usage: test_non_numerical_error() without return types