docs: def destroySingleton(cls):
          """
          Destroys the singleton instance of this class, if one exists.
          """
          singleton_key = '_{0}__singleton'.format(cls.__name__)
          singleton = getattr(cls, singleton_key, None)
          
          if singleton is not None:
              setattr(cls, singleton_key, None)
  
              singleton.close()
              singleton.deleteLater()