public static Artifact @NotNull [] getVersions(URL @NotNull ... urls) {
    Set<Artifact> versions = new HashSet<>();
    for (URL url : urls) {
      final Artifacts allArtifacts = deserialize(url);
      if (allArtifacts != null) {
        final Artifact[] vers = allArtifacts.getArtifacts();
        if (vers != null) {
          versions.addAll(Arrays.asList(vers));
        }
      }
    }

    return versions.toArray(Artifact.EMPTY_ARRAY);
  }
public static Artifact @NotNull [] getVersions(URL @NotNull ... urls)