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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 EnableCronJob(self, cronjob_id):
 """Enables a cronjob."""

    job = self.cronjobs.get(cronjob_id)
    if job is None:
      raise db.UnknownCronJobError("Cron job %s not known." % cronjob_id)
    job.enabled = True