public byte[] toBytes() {
        ByteBuffer buffer = toByteBuffer();
        byte[] bytes = new byte[buffer.remaining()];
        buffer.get(bytes);
        return bytes;
    }
Serialize the bitmap into a flipped ByteBuffer.

@return flipped byte buffer
clickhouse-data/src/main/java/com/clickhouse/data/value/ClickHouseBitmap.java