private void ensureEmptySelectorField(Selector selector, Field field) throws Exception {
        field.setAccessible(true);
        Object obj = field.get(selector);
        if (obj instanceof Collection)
            assertTrue(((Collection<?>) obj).isEmpty(), "Field not empty: " + field + " " + obj);
        else if (obj instanceof Map)
            assertTrue(((Map<?, ?>) obj).isEmpty(), "Field not empty: " + field + " " + obj);
    }
Validate that correct subset of io metrics marked deprecated in docs
clients/src/test/java/org/apache/kafka/common/network/SelectorTest.java