return Collections.emptyList();
    }

    @Override
    public Artifact transformArtifact(Artifact artifact) {
        return artifact;
    }

    @Override
    public Collection<? extends Metadata> finish(Collection<? extends Artifact> artifacts) {
        for (Artifact artifact : artifacts) {
            Object key = VersionsMetadata.getKey(artifact);
            if (processedVersions.get(key) == null) {