code: def testProvideNamedClass_Singleton(self):
      class Foo:
          pass
  
      mod = module.DependencyModule()
      mod.provide_named_class("foo", Foo, singleton=True)
      self.assertIs(mod.get("foo", Foo), mod.get("foo", Foo))
  
imports: import dataclasses
  from typing import Optional, Union
  import tensorflow
  from tfx.utils.di import errors
  from tfx.utils.di import module
label_desc: Use image node_id 20 for calling the ModuleTest obj's underlying member method code with example usage: obj.testProvideNamedClass_Singleton() without return types