<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def cancel(self):
 """Instruct the cluster to cancel the running job. Has no effect if job is not running"""

        if self.status > COMPLETED:
            return
        cmd = self.backend.cmd_cancel(self)
        self._run_cmd(cmd, self.remote, ignore_exit_code=True, ssh=self.ssh)
        self._status = CANCELLED
        self.dump()