private String quote(String string) {
        if (string == null) {
            return null;
        }
        StringBuilder builder = new StringBuilder();
        for (int i = 0; i < string.length(); i++) {
            char ch = string.charAt(i);
            if (ch == '\'') {
                builder.append(ch);
            }
            builder.append(ch);
        }
        return builder.toString();
    }