}

    /**
     * CacheRecord
     */
    class CacheRecord {

        private final Set<Artifact> artifacts;

        private final LifecycleExecutionException exception;

        CacheRecord(Set<Artifact> artifacts) {
            this.artifacts = artifacts;
            this.exception = null;
        }

        CacheRecord(LifecycleExecutionException exception) {

    }

    @Override
    public CacheRecord get(Key key) throws LifecycleExecutionException {
        CacheRecord cacheRecord = cache.get(key);
        if (cacheRecord != null && cacheRecord.getException() != null) {
            throw cacheRecord.getException();
        }
        return cacheRecord;
    }

    @Override
    public CacheRecord put(Key key, Set<Artifact> projectArtifacts) {

        CacheRecord cacheRecord = cache.get(cacheKey);

        if (cacheRecord != null && !cacheRecord.isStale()) {
            Artifact pomArtifact = ArtifactUtils.copyArtifact(cacheRecord.getArtifact());
            Artifact relocatedArtifact = ArtifactUtils.copyArtifactSafe(cacheRecord.getRelocatedArtifact());

        }
    }

    protected final Map<Key, CacheRecord> cache = new ConcurrentHashMap<>();

    @Override
    public Key createKey(List<? extends ClassRealm> extensionRealms) {
        return new CacheKey(extensionRealms);
    }

    public CacheRecord get(Key key) {
        return cache.get(key);
    }

    public CacheRecord put(Key key, ClassRealm projectRealm, DependencyFilter extensionArtifactFilter) {

            DependencyFilter extensionFilter,
            List<RemoteRepository> repositories,
            RepositorySystemSession session);

    CacheRecord get(Key key) throws PluginResolutionException;

    CacheRecord put(Key key, List<Artifact> pluginArtifacts);

    CacheRecord put(Key key, PluginResolutionException e);

    void flush();

    /**

        CacheRecord cacheRecord = cache.get(key);

        if (cacheRecord != null && cacheRecord.getException() != null) {
            throw cacheRecord.getException();
        }

        return cacheRecord;
    }

    public CacheRecord put(Key key, List<Artifact> pluginArtifacts) {
        Objects.requireNonNull(pluginArtifacts, "pluginArtifacts cannot be null");

        assertUniqueKey(key);

            throw new IllegalStateException("Duplicate plugin realm for plugin " + key);
        }

        CacheRecord record = new CacheRecord(pluginRealm, pluginArtifacts);

        cache.put(key, record);

        return record;
    }

    public void flush() {
        for (CacheRecord record : cache.values()) {
            ClassRealm realm = record.getRealm();
            try {

        CacheRecord(ClassRealm realm, DependencyFilter extensionArtifactFilter) {
            this.realm = realm;
            this.extensionArtifactFilter = extensionArtifactFilter;
        }
    }

    Key createKey(List<? extends ClassRealm> extensionRealms);

    CacheRecord get(Key key);

     */
    interface Key {
        // marker interface for cache keys
    }

    /**
     * CacheRecord
     */
    class CacheRecord {

        private final ClassRealm realm;

        private final ExtensionDescriptor descriptor;

        private final List<Artifact> artifacts;

        CacheRecord(ClassRealm realm, ExtensionDescriptor descriptor, List<Artifact> artifacts) {
            this.realm = realm;

        }
    }

    protected final Map<Key, CacheRecord> cache = new ConcurrentHashMap<>();

    @Override
    public Key createKey(List<Artifact> extensionArtifacts) {
        return new CacheKey(extensionArtifacts);
    }

    public CacheRecord get(Key key) {
        return cache.get(key);
    }

    public CacheRecord put(