anchor.diff:          }
         }
         else if (record["action"] == "remove") {
  -        logger.info("ACTION REMOVE");
           if (beforeLeqPivot(record)) {
             collectionLength--;
             diff.add(remove(record));
  
positive.code:     beforeOrAfter.forEach((record) {
        version = record["version"];
        if (record["action"] == "add") {
          logger.info("ACTION ADD");
          if (afterLeqPivot(record)) {
            collectionLength++;
            diff.add(add(record));
  
negative.code:     });
    }
  
    Future writeOperation(String _id, String author, String action, Map newData) {
      num nextVersion;
      return _get_locks()
        .then((_) => collection.findOne({"_id" : _id}))
        .then((Map oldData) {
  
  