text: # Reference cycles involving only the ob_type field are rather uncommon
  # but possible.  Inspired by SF bug 1469629.
  
  import gc
  
  def leak():
      class T(type):
          pass
      class U(type, metaclass=T):
          pass
      U.__class__ = U
      del U
      gc.collect(); gc.collect(); gc.collect()
  