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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 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