@NonNull
    @Override
    public SpannableBuilder append(CharSequence csq, int start, int end) {

        final CharSequence cs = csq.subSequence(start, end);
        copySpans(length(), cs);

        builder.append(cs);

        return this;
    }
@ NonNull @ Override public SpannableBuilder append ( CharSequence csq , int start , int end ) { final CharSequence cs = csq . subSequence ( start , end ) ; copySpans ( length ( ) , cs ) ; builder . append ( cs ) ; return this ; }
@since 2.0.0 to follow Appendable interface