default <K> Seq<Tuple2<K, Seq<T>>> grouped(Function<? super T, ? extends K> classifier) {
        return grouped(this, classifier);
    }
Classify this stream's elements according to a given classifier function.
<p>
<pre><code>
// Seq(tuple(1, Seq(1, 3, 5)), tuple(0, Seq(2, 4, 6)))
Seq.of(1, 2, 3, 4, 5, 6).grouped(i -> i % 2)
// Seq(tuple(true, Seq(1, 3, 5)), tuple(false, Seq(2, 4, 6)))
Seq.of(1, 2, 3, 4, 5, 6).grouped(i -> i % 2 != 0)
</code></pre>

This is a non-terminal analog of {@link #groupBy(Function)})
@see #groupBy(Function)
@see #partition(Predicate)
jOOL-java-8/src/main/java/org/jooq/lambda/Seq.java