* If multiple extractors are associated with the key, returns a composite extractor
     * that tries each extractor in order until one succeeds.
     *
     * @param key the key to look up
     * @return the extractor for the key, or null if not found
     */
    public Extractor getExtractor(final String key) {
        final Extractor[] extractors = extractorMap.get(key);

            }
        }

        return matchedDirective;
    }

    /**
     * Retrieves the robots.txt directive for the specified user agent.
     *
     * @param userAgent The user agent string to look up in the directives
     * @return The Directive object matching the user agent, or null if no matching directive is found or if userAgent is null
     */
    public Directive getDirective(final String userAgent) {