this.packages = Collections.unmodifiableSet(new HashSet<>(packages));
        this.key = key;
        this.configuration = configuration;
    }

    /**
     * Returns ClassLoader used to load extension classes.
     */
    public ClassRealm getClassRealm() {
        return realm;
    }

    /**
     * Returns artifacts exported by the extension, identified by groupId:artifactId string key.
     */