private static Map<String, String> union(Map<String, String> a, Map<String, String> b) {
        if (a.isEmpty()) {
            return b;
        } else if (b.isEmpty()) {
            return a;
        } else {
            Map<String, String> union = new HashMap<>();
            union.putAll(a);
            union.putAll(b);
            return union;
        }
    }
Fuzzy unquoting mechanism that works also with somewhat malformed
quotes.

@param s string to unquote
@return unquoted string
tika-core/src/main/java/org/apache/tika/mime/MediaType.java