code: def test_single_column_dataframe_unnamed(self):
      r_f, y_true = self._get_raw_data()
      raw_feature = pd.DataFrame(data=r_f)
  
      target = _get_raw_MetricFrame()
      msg = "DataFrame column names must be strings. Name '0' is of type <class 'int'>"
      with pytest.raises(ValueError) as execInfo:
          _ = target._process_features("Unused", raw_feature, y_true)
      assert execInfo.value.args[0] == msg
  
imports: import numpy
  import pandas
  import pytest
  import fairlearn.metrics
  from .utils import _get_raw_MetricFrame
label_desc: Use image node_id 8 for calling the TestSingleFeature obj's underlying member method code with example usage: obj.test_single_column_dataframe_unnamed() without return types