let retry = true;
        while (retry) {
            const t = await sequelize.transaction({
                isolationLevel: Transaction.ISOLATION_LEVELS.SERIALIZABLE
            });
            try {
                let id = await the_function_that_actually_does_the_work(t);
                await t.commit();
                retry = false;
            } catch (err) {
                retry = is_serialization_failure(err); // serialization failures should be retried
                if (!is_rollback_failure(err)) {
                    await t.rollback();
                }   // else transaction has already been rolled back and you should NOT roll it back again!
                if (!retry) {
                    throw err;  // re-throw so caller knows we failed
                }   
            }
        }

export const is_serialization_failure = (e): boolean => {
    // https://www.postgresql.org/docs/current/mvcc-serialization-failure-handling.html
    // The optional chaining (?.) operator accesses an object's property or calls a function.
    // If the object accessed or function called using this operator is undefined or null, 
    // the expression short circuits and evaluates to undefined instead of throwing an error.
    // more accurately only 40001 is serialization failure. 40P01 is a deadlock failure.
    return (e.original?.code === '40001' || e.original?.code === '40P01');
}

export const is_rollback_failure = (e): boolean => {
    // https://www.postgresql.org/docs/current/errcodes-appendix.html
    return e.original?.code?.startsWith('40');    
}