def send(self, transactions):
        """ Package up transactions into a batch and send them to the
        network via the provided batch_sender.
        :param transactions: list of transactions to package and broadcast.
        :return: None
        """
        txn_signatures = [txn.header_signature for txn in transactions]
        header = BatchHeader(
            signer_public_key=self._identity_signer.get_public_key().as_hex(),
            transaction_ids=txn_signatures
        ).SerializeToString()

        signature = self._identity_signer.sign(header)
        batch = Batch(
            header=header,
            transactions=transactions,
            header_signature=signature)

        self._batch_sender.send(batch)
Package up transactions into a batch and send them to the
        network via the provided batch_sender.
        :param transactions: list of transactions to package and broadcast.
        :return: None