Common implementation for the peek_* functions

def _peek_common(self, typ):
        """Common implementation for the peek_* functions"""
        with self._sock_ctx() as socket:
            self._send_message('peek-{0}'.format(typ), socket)
            job_id, job_data = self._receive_id_and_data_with_prefix(b'FOUND', socket)
            return Job(job_id, job_data)