code: def test__df_index_name_with_unnamed_index(self) -> None:
      df = pd.DataFrame(dict(a=[10], b=[20], c=[30]))
      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 28 for calling the TestColumnDataSource obj's underlying member method code with example usage: obj.test__df_index_name_with_unnamed_index() without return types