code: def test_unnamed_dataframe(self):
      a, b, y_true = self._get_raw_data()
  
      rf = pd.DataFrame(data=zip(a, b))
  
      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", rf, 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 6 for calling the TestTwoFeatures obj's underlying member method code with example usage: obj.test_unnamed_dataframe() without return types