/**
     * Gets the values associated with a given key from the metadata.
     *
     * @param key the metadata key
     * @return the values associated with the key, or null if not found
     */
    public String[] getValues(final String key) {
        return metadata.get(key);
    }

    /**
     * Gets the set of all metadata keys.
     *
     * @return the set of metadata keys
     */