'Returns the Job that matches the given ``job_id``.
:param str|unicode job_id: the identifier of the job
:param str|unicode jobstore: alias of the job store that most likely contains the job
:return: the Job by the given ID, or ``None`` if it wasn\'t found
:rtype: Job'

def get_job(self, job_id, jobstore=None):

    with self._jobstores_lock:
        try:
            return self._lookup_job(job_id, jobstore)[0]
        except JobLookupError:
            return
