docs: def export_batch(self):
          """Returns a batch instance after exporting a batch of txs.
          """
          batch = self.batch_cls(
              model=self.model, history_model=self.history_model, using=self.using
          )
          if batch.items:
              try:
                  json_file = self.json_file_cls(batch=batch, path=self.path)
                  json_file.write()
              except JSONDumpFileError as e:
                  raise TransactionExporterError(e)
              batch.close()
              return batch
          return None