@Override
 public boolean equals(Object obj) {
   if (obj == null) {
     return false;
   }
   if (obj instanceof ModificationRecordImpl) {
     ModificationRecordImpl that = (ModificationRecordImpl) obj;
     return Utils.equals(this.lastModified, that.lastModified)
         && Utils.equals(this.lastModifiedBy, that.lastModifiedBy);
   }
   return false;
 }