code: def subscribeLeader(self, vehID, dist=0., begin=0, end=2**31 - 1):
          
          self._connection._subscribe(tc.CMD_SUBSCRIBE_VEHICLE_VARIABLE, begin, end, vehID,
                                      (tc.VAR_LEADER,), {tc.VAR_LEADER: struct.pack("!Bd", tc.TYPE_DOUBLE, dist)})
docs: subscribeLeader(string, double) -> None
  
          Subscribe for the leading vehicle id together with the distance.
          The dist parameter defines the maximum lookahead, 0 calculates a lookahead from the brake gap.