@Override
    public boolean cancel(boolean mayInterruptIfRunning) {
        throw new UnsupportedOperationException();
    }
<p>Closes the underlying {@link ContentChannel}. If {@link CompletionHandler#failed(Throwable)} is called,
either of the get() methods will rethrow that Throwable.</p>
jdisc_core/src/main/java/com/yahoo/jdisc/handler/FastContentWriter.java