public static boolean isKnownExtension(final String extension) {
        if (NullSafe.isEmptyString(extension)) {
            return false;
        } else {
            return EXTENSION_MAP.containsKey(extension.toLowerCase(Locale.ROOT));
        }
    }
@return True if the passed extension is one known to stroom
stroom-data/stroom-data-zip/src/main/java/stroom/data/zip/StroomZipFileType.java