code: def denormalize_volume(volume):
          '''convert volume metadata from archivant to es format'''
          id = volume.get('id', None)
          res = dict()
          res.update(volume['metadata'])
          denorm_attachments = list()
          for a in volume['attachments']:
              denorm_attachments.append(Archivant.denormalize_attachment(a))
          res['_attachments'] = denorm_attachments
          return id, ref denormalize_volume(volume):
          '''convert volume metadata from archivant to es format'''
          id = volume.get('id', None)
          res = dict()
          res.update(volume['metadata'])
          denorm_attachments = list()
          for a in volume['attachments']:
              denorm_attachments.append(Archivant.denormalize_attachment(a))
          res['_attachments'] = denorm_attachments
          return id, res
docs: convert volume metadata from archivant to es format