default Seq<Tuple2<T, T>> innerSelfJoin(BiPredicate<? super T, ? super T> predicate) {
        SeqBuffer<T> buffer = SeqBuffer.of(this);
        return buffer.seq().innerJoin(buffer.seq(), predicate);
    }
Inner join stream with itself.
<p>
<pre><code>
// (tuple(1, 1), tuple(2, 2))
Seq.of(1, 2).innerSelfJoin((t, u) -> Objects.equals(t, u))
</code></pre>
jOOL-java-8/src/main/java/org/jooq/lambda/Seq.java