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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 get_traceback(db, job_id):
 """ Return the traceback of the given calculation as a list of lines. The list is empty if the calculation was successful. :param db: a :class:`openquake.server.dbapi.Db` instance :param job_id: a job ID """

    # strange: understand why the filter returns two lines or zero lines
    log = db("SELECT * FROM log WHERE job_id=?x AND level='CRITICAL'",
             job_id)
    if not log:
        return []
    response_data = log[-1].message.splitlines()
    return response_data