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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 mark_job_as_completed(job_id, data=None):
 """Mark a job as completed successfully. :param job_id: the job_id of the job to be updated :type job_id: unicode :param data: the output data returned by the job :type data: any JSON-serializable type (including None) """

    update_dict = {
        "status": "complete",
        "data": json.dumps(data),
        "finished_timestamp": datetime.datetime.now(),
    }
    _update_job(job_id, update_dict)