How to use the traci.close function in traci

traci.vehicle.changeLane(vehID, laneIndex, traciEndTime)

        # check if vehID has arrived at destination
        arrivedList = traci.simulation.getArrivedIDList()
        if vehID in arrivedList:
            print("[%03d] Vehicle '%s' has arrived at destination" % (step, vehID))
            break

        print("[%03d] lane %d, lateral pos: %.2f" %
              (step, traci.vehicle.getLaneIndex(vehID), traci.vehicle.getLateralLanePosition(vehID)))
        sys.stdout.flush()

        step += 1

    print("Print ended at step %s" % traci.simulation.getTime())
    traci.close()
    sys.stdout.flush()

# this is the normal way of using traci. sumo is started as a
    # subprocess and then the python script connects and runs
    traci.start([sumoBinary, "-n", "input_net.net.xml", "-r", "input_routes.rou.xml",
                 "--no-step-log", "true",
                 "--default.speeddev", "0"])

    # Wait until the vehicle enters
    while ToC_vehicle not in traci.vehicle.getIDList():
        traci.simulationStep()

    printToCParams(ToC_vehicle, extra=True)

    run()

    traci.close()
    sys.stdout.flush()

# print(traci.vehicle.getDecel("veh2") ,"== 2.0")
# print(traci.vehicle.getAccel("veh2") ,"== 3.0")
print(traci.vehicle.getLength("veh2"), "== 4.0")
# print(traci.vehicle.getApparentDecel("veh2") , "== 6.0")
# print(traci.vehicle.getEmergencyDecel("veh2") , "== 7.0")
# print(traci.vehicle.getEmissionClass("veh2") , " == ??")
print(traci.vehicle.getMinGap("veh2"), "== 0.8")
print(traci.vehicle.getSpeedFactor("veh2"), "== 0.9")
print(traci.vehicle.getWidth("veh2"), "== 3.3")
# print(traci.vehicle.getTau("veh2") , "== 1.3")
print(traci.vehicle.getMaxSpeed("veh2"), "== 99.9")
print(traci.vehicle.getActionStepLength("veh2"), "==1.5")

while traci.simulation.getTime() < tend:
    traci.simulationStep()
traci.close()

remaining = traci.person.getRemainingStages("p3")
assert(remaining == 1)
# replace current stage
print_remaining_plan("p3", "(before replacement of current stage")
traci.person.replaceStage("p3", 0, stage2)
print_remaining_plan("p3", "(after replacement")
# replace later stage
traci.person.appendStage("p3", stage3)
print_remaining_plan("p3", "(before replacement of next stage")
traci.person.replaceStage("p3", 1, stage4)
print_remaining_plan("p3", "(after replacement")

for i in range(41):
    traci.simulationStep()

traci.close()

step = 1
    nrEnteredVehicles = 0
    sumoStop = False
    try:
        traciEndStep = math.ceil(traciEndTime / steplength)
        while not step > traciEndStep:
            traci.simulationStep(step * steplength)
            # print(index, "asking for vehicles")
            # sys.stdout.flush()
            traci.vehicle.getIDList()
            nrEnteredVehicles += traci.simulation.getDepartedNumber()
            # ~ print(index, "Newly entered vehicles: ", traci.simulation.getDepartedNumber(), "(vehs: ", vehs, ")")
            # ~ sys.stdout.flush()
            step += 1
        endTime = traci.simulation.getTime()
        traci.close()
    except traci.FatalTraCIError as e:
        if str(e) == "connection closed by SUMO":
            time.sleep(orderTime * index)  # assure ordering of outputs
            sumoStop = True
            print("client %s: " % index, str(e), " (at TraCIStep %s)" % step)
            sys.stdout.flush()
        else:
            raise
    if not sumoStop:
        time.sleep(orderTime * index)  # assure ordering of outputs
        print("Process %s ended at step %s" % (index, endTime))
        print("Process %s was informed about %s entered vehicles" % (index, nrEnteredVehicles))
        sys.stdout.flush()

def reset(self):
        """
        Resets the state of the environment, returning an initial observation.
        Outputs
        -------
        observation : the initial observation of the space. (Initial reward is assumed to be 0.)
        """
        # self state is velocity, observation is velocity
        # self._state = np.random.uniform(0, self.GOAL_VELOCITY, size=(self.num_cars,))
        # print("In reset function", self.initialized)
        if self.initialized:
            traci.close()
        sumoProcess = subprocess.Popen([self.sumoBinary, "-c", self.cfgfn, "--remote-port", str(self.PORT)], stdout=sys.stdout, stderr=sys.stderr)
        traci.init(self.PORT)
        traci.simulationStep()
        if not self.initialized:
            self.vehIDs = traci.vehicle.getIDList()
            print("ID List in reset", self.vehIDs)
            self.initialized = True
        self._state = np.array([traci.vehicle.getSpeed(vID) for vID in self.controllable])
        observation = np.copy(self._state)
        return observation

def disconnect(self):
        self.isConnected = False
        traci.close()
        sys.stdout.flush()

def terminate(self):
        super(SimpleVelocityEnvironment, self).terminate()
        traci.close()

def cleanup_sumo_simulation(simulation_task):
    global last_lights, last_vehicles
    if simulation_task:
        if simulation_task.cancel():
            simulation_task = None
        last_vehicles = {}
        last_lights = {}
        traci.close()

#
        set_sumo_inputs()

        #
        open_tlc(step)
        # open_tlc(step, amber_state)

        #
        set_state()

        #
        step += 1

    #
    traci.close()
    sys.stdout.flush()