code: def test_field(self) -> None:
      class Foo(HasProps):
          x = bcpd.NumberSpec("xfield")
  
      f = Foo()
      assert f.x == "xfield"
      assert Foo.__dict__["x"].get_value(f) == Field("xfield")
      f.x = "my_x"
      assert f.x == "my_x"
      assert Foo.__dict__["x"].get_value(f) == Field("my_x")
  
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 1 for calling the Test_NumberSpec obj's underlying member method code with example usage: obj.test_field() without return types