Create a JWT with one or more keys.
        Returns a compact-form serialized JWT if there is only one key to sign with
        Returns a JSON-structured serialized JWT if there are multiple keys to sign with

def sign(self, payload, signing_key_or_keys):
        """
        Create a JWT with one or more keys.
        Returns a compact-form serialized JWT if there is only one key to sign with
        Returns a JSON-structured serialized JWT if there are multiple keys to sign with
        """
        if isinstance(signing_key_or_keys, list):
            return self._sign_multi(payload, signing_key_or_keys)

        else:
            return self._sign_single(payload, signing_key_or_keys)