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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_key_by_job_id(cls, mapreduce_id):
 """Retrieves the Key for a mapreduce ID. Args: mapreduce_id: The job to fetch. Returns: Datastore Key for the command for the given job ID. """

    return db.Key.from_path(cls.kind(), "%s:%s" % (mapreduce_id, cls._KEY_NAME))