@Override
    public ByteBuf duplicate() {
        ensureAccessible();
        return new UnpooledDuplicatedByteBuf(this);
    }
@Test
    public void testRetainedDuplicateAfterReleaseDuplicate() {
        ByteBuf buf = newBuffer(1);
        ByteBuf buf2 = buf.duplicate();
        assertRetainedDuplicateFailAfterRelease(buf, buf2);
    }