code: def test_multiclasslabel_non_positive_label_error():
      df = pd.DataFrame({"a": [0], "b": [0.5], "c": ["x"]})
      with pytest.raises(ValueError) as value_error:
          DFtoVW(
              df=df,
              label=MulticlassLabel(label="a", weight="b"),
              features=Feature("c"),
          )
      expected = "In argument 'label' of 'MulticlassLabel', column 'a' must be >= 1."
      assert expected == str(value_error.value)
  
imports: import pytest
  import pandas
  from vowpalwabbit.dftovw import ContextualbanditLabel, DFtoVW, Feature, MulticlassLabel, MultiLabel, Namespace, SimpleLabel
label_desc: Use image node_id 22 for calling a global function with example usage: test_multiclasslabel_non_positive_label_error() without return types