code: def test_assign_none_to_enum_or_none(self):
      class Example2(HasTraits):
          color = UseEnum(Color, allow_none=True)
  
      example = Example2()
      example.color = None
      self.assertIs(example.color, None)
  
imports: import enum
  import unittest
  from traitlets import CaselessStrEnum, Enum, FuzzyEnum, HasTraits, TraitError, UseEnum
label_desc: Use image node_id 16 for calling the TestUseEnum obj's underlying member method code with example usage: obj.test_assign_none_to_enum_or_none() without return types