# Edges can have labels, too:
 [ Kempten ] - Bahn -> [ Schongau ]             # normal edge
 [ Schongau ] -Auto-> [ Regensburg ]            # ditto
 [ Regensburg ] - Fahrrad - > [ Roth ]          # dashed
 [ Regensburg ] = Motorrad => [ Straubing ]     # double
