public LegacyFilterConfig getSubConfig(final String key) {
        final LegacyFilterConfig subConfig = new LegacyFilterConfig();
        subConfig.putDefaultList(this.get(key));
        return subConfig;
    }
creates a new config object, taking the content of one key of this config and putting it into the default list
main/src/main/java/cgeo/geocaching/utils/config/LegacyFilterConfig.java