@Override
    default Seq<T> parallel() {
        return this;
    }
Seq streams are always sequential and, as such, doesn't support
parallelization.

@return this sequential stream unmodified
@see <a href="https://github.com/jOOQ/jOOL/issues/130">jOOL Issue #130</a>
jOOL/src/main/java/org/jooq/lambda/Seq.java