default <U> Seq<U> ofType(Class<? extends U> type) {
        return ofType(this, type);
    }
Keep only those elements in a stream that are of a given type.
<p>
<pre><code>
// (1, 2, 3)
Seq.of(1, "a", 2, "b", 3).ofType(Integer.class)
</code></pre>

@see #ofType(Stream, Class)
jOOL-java-8/src/main/java/org/jooq/lambda/Seq.java