static Charset charset(String contentType) {
        if (contentType != null) {
            Matcher matcher = charsetPattern.matcher(contentType);
            if (matcher.find()) {
                try {
                    return Charset.forName(matcher.group(1));
                } catch (UnsupportedCharsetException uce) {
                    return Utf8.getCharset();
                }
            }
        }
        return Utf8.getCharset();
    }
Returns a mutable multi-map of headers for this Response.

@return a mutable multi-map of headers for this Response
application/src/main/java/com/yahoo/application/container/handler/Response.java