@Override
    public <K> Map<K, T> toMap(Function<? super T, ? extends K> keyMapper) {
        return toMap(keyMapper, Function.identity());
    }
Always returns false. Seq streams are always sequential and, as such,
doesn't support parallelization.

@return false
@see <a href="https://github.com/jOOQ/jOOL/issues/130">jOOL Issue #130</a>
jOOL-java-8/src/main/java/org/jooq/lambda/SeqImpl.java