code: def test_fields(self) -> None:
      class Foo(HasProps):
          x = bcpd.FontSizeSpec(default="0px")
  
      a = Foo()
  
      a.x = "_120"
      assert a.x == "_120"
  
      a.x = dict(field="_120")
      assert a.x == field("_120")
  
      a.x = "foo"
      assert a.x == "foo"
  
      a.x = dict(field="foo")
      assert a.x == field("foo")
  
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 3 for calling the Test_FontSizeSpec obj's underlying member method code with example usage: obj.test_fields() without return types