@Override
    public CharSequence getCharSequence(int index, int length, Charset charset) {
        checkIndex(index, length);
        return null;
    }
@Test
    public void testGetCharSequence() {
        EmptyByteBuf empty = new EmptyByteBuf(UnpooledByteBufAllocator.DEFAULT);
        assertEquals("", empty.readCharSequence(0, CharsetUtil.US_ASCII));
    }