docs: def filter_creation_date(groups, start, end):
      """Filter log groups by their creation date.
  
      Also sets group specific value for start to the minimum
      of creation date or start.
      """
      results = []
      for g in groups:
          created = datetime.fromtimestamp(g['creationTime'] / 1000.0)
          if created > end:
              continue
          if created > start:
              g['exportStart'] = created
          else:
              g['exportStart'] = start
          results.append(g)
      return results