from_stop_id,to_stop_id,transfer_type,min_transfer_time
stop1a,stop1b,2,10
stop1b,stop1a,2,10
stop3a,stop3b,2,10
stop3b,stop3a,2,10
stop8a,stop8b,2,10
stop8b,stop8a,2,10
stop2,stop5,3,