code: def test_Singleton():
      class MySingleton(Basic, metaclass=Singleton):
          pass
  
      MySingleton()  # force instantiation
      assert MySingleton() is not Basic()
      assert MySingleton() is MySingleton()
      assert S.MySingleton is MySingleton()
  
      class MySingleton_sub(MySingleton):
          pass
  
      MySingleton_sub()
      assert MySingleton_sub() is not MySingleton()
      assert MySingleton_sub() is MySingleton_sub()
  
imports: from sympy.core.basic import Basic
  from sympy.core.numbers import Rational
  from sympy.core.singleton import S, Singleton
label_desc: Use image node_id 1 for calling a global function with example usage: test_Singleton() without return types