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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 DeleteOldRuns(self, cutoff_timestamp=None):
 """Deletes runs that were started before the timestamp given."""

    if cutoff_timestamp is None:
      raise ValueError("cutoff_timestamp can't be None")

    return data_store.REL_DB.DeleteOldCronJobRuns(
        cutoff_timestamp=cutoff_timestamp)