/** Removes revoked and invalid photo attributes from a photo attribute array. */
 private PhotoAttribute[] filterArray(PhotoAttribute[] original) {
   List<PhotoAttribute> filtered = new ArrayList<>();
   for (PhotoAttribute att : original) {
     if (!att.isRevokedOrInvalid()) {
       filtered.add(att);
     }
   }
   return filtered.toArray(new PhotoAttribute[filtered.size()]);
 }