db.timetable.updateMany(
   {},
   { $rename: { 'Train No': 'trainNo', 'Train Name': 'trainName', 'SEQ':'seq', 'Station Code':'stationCode', 'Station Name': 'stationName', 'Arrival time':'arrivalTime', 'Departure Time':'departureTime', 'Distance':'distance', 'Source Station':'sourceStation','Source Station Name':'sourceStationName', 'Destination Station':'destinationStation','Destination Station Name':'destinationStationName'  } }
)