code: def test__df_index_name_with_unnamed_multi_index(self) -> None:
      arrays = [
          np.array(
              ["bar", "bar", "baz", "baz", "foo", "foo", "qux", "qux"]
          ),
          np.array(
              ["one", "two", "one", "two", "one", "two", "one", "two"]
          ),
      ]
      df = pd.DataFrame(np.random.randn(8, 4), index=arrays)
      assert df.index.names == [None, None]
      assert bms.ColumnDataSource._df_index_name(df) == "index"
  
imports: from __future__ import annotations
  import pytest
  import datetime
  import io
  import numpy
  import pandas
  from bokeh.models import Selection
  from bokeh.util.serialization import convert_datetime_array
  from bokeh.util.warnings import BokehDeprecationWarning
  import bokeh.models.sources
label_desc: Use image node_id 30 for calling the TestColumnDataSource obj's underlying member method code with example usage: obj.test__df_index_name_with_unnamed_multi_index() without return types