code: def test_named_value(self) -> None:
      class Foo(HasProps):
          col = bcpd.ColorSpec("colorfield")
  
      desc = Foo.__dict__["col"]
      f = Foo()
  
      f.col = "red"
      assert f.col == "red"
      assert desc.get_value(f) == Value("red")
      f.col = "forestgreen"
      assert f.col == "forestgreen"
      assert desc.get_value(f) == Value("forestgreen")
  
imports: from __future__ import annotations
  import pytest
  import datetime
  import warnings
  from copy import copy
  import numpy
  import pandas
  from bokeh.core.has_props import HasProps, Local
  from bokeh.core.property.vectorization import Field, Value, field, value
  from tests.support.util.api import verify_all
  import bokeh.core.property.dataspec
label_desc: Use image node_id 5 for calling the Test_ColorSpec obj's underlying member method code with example usage: obj.test_named_value() without return types