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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def create_job(db, datadir):
 """ Create job for the given user, return it. :param db: a :class:`openquake.server.dbapi.Db` instance :param datadir: Data directory of the user who owns/started this job. :returns: the job ID """

    calc_id = get_calc_id(db, datadir) + 1
    job = dict(id=calc_id, is_running=1, description='just created',
               user_name='openquake', calculation_mode='to be set',
               ds_calc_dir=os.path.join('%s/calc_%s' % (datadir, calc_id)))
    return db('INSERT INTO job (?S) VALUES (?X)',
              job.keys(), job.values()).lastrowid