code: def variantsGenerator(self, request):
          
          compoundId = datamodel.VariantSetCompoundId \
              .parse(request.variant_set_id)
          dataset = self.getDataRepository().getDataset(compoundId.dataset_id)
          variantSet = dataset.getVariantSet(compoundId.variant_set_id)
          intervalIterator = paging.VariantsIntervalIterator(
              request, variantSet)
          return intervalIterator
docs: Returns a generator over the (variant, nextPageToken) pairs defined
          by the specified request.