Check if the mimetype indicates JSON data, either
        :mimetype:`application/json` or :mimetype:`application/*+json`.

def is_json(self):
        """Check if the mimetype indicates JSON data, either
        :mimetype:`application/json` or :mimetype:`application/*+json`.
        """
        mt = self.mimetype
        return (
            mt == "application/json"
            or mt.startswith("application/")
            and mt.endswith("+json")
        )