def METHOD_NAME(self, name, value):
    if name == "thisown":
        self.this.own(value)
    elif name == "this":
        set(self, name, value)
    elif hasattr(self, name) and isinstance(getattr(type(self), name), property):
        set(self, name, value)
    else:
        raise AttributeError("You cannot add instance attributes to %s" % self)