anchor.diff:          var value = result['value']['seq'];
           completer.complete(value);
         }
  -    })
  -    .catchError((e) {
  +    }).catchError((e) {
         log.shout('Get next sequence error:', e);
         completer.completeError(e);
       });
  
positive.code:     List found = new List();
      var mongoSelector = null;
  
      _connection.listCollections()
      .then((List collections) {
        if (!collections.contains(select.table.tableName)) {
          throw new TableNotExistException();
        }
  
        return _connection.collection(select.table.tableName);
      })
      .then((collection) {
        if (select.condition != null) {
          mongoSelector = convertCondition(select.table, select.condition);
        }
  
negative.code:     log.finest('Create sequence:' + table.toString() + ' ' + field.toString());
      var countersCollection = await _connection.collection('counters');
  
      var existingCounter = await countersCollection.findOne(mongo_connector.where
          .eq('_id', "${table.tableName}_${field.fieldName}_seq"));
      if (existingCounter == null) {
        var insertResult = await countersCollection.insert(
            {'_id': "${table.tableName}_${field.fieldName}_seq", 'seq': 0});
  
        log.finest('Create sequence insert result:', insertResult);
      }
  