code: def test_selected_serialized(self) -> None:
      ds = bms.ColumnDataSource()
      prop = ds.lookup("selected")
      assert prop.serialized is True
  
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 3 for calling the TestColumnDataSource obj's underlying member method code with example usage: obj.test_selected_serialized() without return types