anchor.diff:    num _limit = NOLIMIT;
     num _skip = NOSKIP;
     Cache cache;
  +  IdGenerator idgen;
   
     //for testing purposes
     Future<int> get maxVersion => _maxVersion;
  
positive.code:         if(jsonData is List) {
            if(jsonData[0] == CLEAN_UNDEFINED){
              action = 'add';
            }
            else if(jsonData[1] == CLEAN_UNDEFINED){
              action = 'remove';
  
negative.code:       .catchError((e, s) => _release_locks().then((_) => _processError(e, s)));
    }
  
    static ensureId(Map doc, IdGenerator idgen) {
      if (!doc.containsKey('_id')) doc['_id'] = idgen.next();
    }
  
    static stripCollectionName(Map doc){
      //modifikuje doc
      if (doc.containsKey(COLLECTION_NAME)) doc.remove(COLLECTION_NAME);
  