def change_content_type(self, new_ctype, guess=False):
        """
        Copies object to itself, but applies a new content-type. The guess
        feature requires the container to be CDN-enabled. If not then the
        content-type must be supplied. If using guess with a CDN-enabled
        container, new_ctype can be set to None.
        Failure during the put will result in a swift exception.
        """
        self.container.change_object_content_type(self, new_ctype=new_ctype,
                guess=guess)