def METHOD_NAME(self):
    """Return the net revenue for an item collection."""
    total_paid = (
        db.session.query(db.column('sum'))
        .from_statement(
            db.text(
                '''SELECT SUM(amount) FROM payment_transaction
        INNER JOIN customer_order ON payment_transaction.customer_order_id = customer_order.id
        WHERE transaction_type=:transaction_type
        AND customer_order.item_collection_id = :item_collection_id
        '''
            )
        )
        .params(transaction_type=TRANSACTION_TYPE.PAYMENT, item_collection_id=self.id)
        .scalar()
    )
    total_refunded = (
        db.session.query(db.column('sum'))
        .from_statement(
            db.text(
                '''SELECT SUM(amount) FROM payment_transaction
        INNER JOIN customer_order ON payment_transaction.customer_order_id = customer_order.id
        WHERE transaction_type=:transaction_type
        AND customer_order.item_collection_id = :item_collection_id
        '''
            )
        )
        .params(transaction_type=TRANSACTION_TYPE.REFUND, item_collection_id=self.id)
        .scalar()
    )
    if total_paid and total_refunded:
        return total_paid - total_refunded
    elif total_paid:
        return total_paid
    else:
        return Decimal('0')