code: def _list_superclasses(class_def):
      
      superclasses = class_def.get('superClasses', [])
      if superclasses:
          # Make sure to duplicate the list
          return list(superclasses)
  
      sup = class_def.get('superClass', None)
      if sup:
          return [sup]
      else:
          return []
docs: Return a list of the superclasses of the given class