Add an :class:`Operation <stellar_base.operation.Operation>` to
        this transaction.

        This method will only add an operation if it is not already in the
        transaction's list of operations, i.e. every operation in the
        transaction should be unique.

        :param Operation operation: The operation to add to this transaction.

def add_operation(self, operation):
        """Add an :class:`Operation <stellar_base.operation.Operation>` to
        this transaction.

        This method will only add an operation if it is not already in the
        transaction's list of operations, i.e. every operation in the
        transaction should be unique.

        :param Operation operation: The operation to add to this transaction.

        """
        if operation not in self.operations:
            self.operations.append(operation)