public IDatabaseReader <TripId, Trip> GetTripsReader()
        {
            var readers =
                All().Select(tdb => tdb.TripsDb);

            return(DatabaseEnumeratorAggregator <TripId, Trip> .CreateFrom(readers));
        }
        public IDatabaseReader <ConnectionId, Connection> GetConnectionsReader()
        {
            var readers = All().Select(tdb => tdb.ConnectionsDb);

            return(DatabaseEnumeratorAggregator <ConnectionId, Connection> .CreateFrom(readers));
        }