return Collections.unmodifiableCollection(attached);
    }

    @Override
    @Nonnull
    public Collection<ProducedArtifact> getAllArtifacts(@Nonnull Project project) {
        requireNonNull(project, "project cannot be null");
        ArrayList<ProducedArtifact> result = new ArrayList<>(2);
        result.addAll(project.getArtifacts());