public void verifySelectorEmpty(Selector selector) throws Exception {
        for (KafkaChannel channel : selector.channels()) {
            selector.close(channel.id());
            assertNull(channel.selectionKey().attachment());
        }
        selector.poll(0);
        selector.poll(0); // Poll a second time to clear everything
        ensureEmptySelectorFields(selector);
    }
Validate that correct subset of io metrics marked deprecated in docs
clients/src/test/java/org/apache/kafka/common/network/SelectorTest.java