code: def del_instance(self, obj):
          
          to_remove = set()
          for wrkey, _obj in self.iter_instances():
              if obj is _obj:
                  to_remove.add(wrkey)
          for wrkey in to_remove:
              del self[wrkey]
docs: Remove any stored instance methods that belong to an object
  
          Args:
              obj: The instance object to remove