@Override
        @Nullable
        public String getNamespaceURI(String prefix, XmlElement context) {
            final String s = myMap.get(prefix);
            if (s == null && prefix.length() == 0) {
                return "";
            }
            return s;
        }
@Override
        @Nullable
        public String getNamespaceURI(String prefix, XmlElement context)