Returns a Transaction object from the block store by its id.

        Params:
            transaction_id (str): The header_signature of the desired txn

        Returns:
            Transaction: The specified transaction

        Raises:
            ValueError: The transaction is not in the block store

def get_transaction(self, transaction_id):
        """Returns a Transaction object from the block store by its id.

        Params:
            transaction_id (str): The header_signature of the desired txn

        Returns:
            Transaction: The specified transaction

        Raises:
            ValueError: The transaction is not in the block store
        """
        payload = self._get_data_by_id(
            transaction_id, 'commit_store_get_transaction')

        txn = Transaction()
        txn.ParseFromString(payload)

        return txn