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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def start(self):
 """ Start the GNS3 VM. """


        # get a NAT interface number
        nat_interface_number = yield from self._look_for_interface("nat")
        if nat_interface_number < 0:
            raise GNS3VMError("The GNS3 VM: {} must have a NAT interface configured in order to start".format(self.vmname))

        hostonly_interface_number = yield from self._look_for_interface("hostonly")
        if hostonly_interface_number < 0:
            raise GNS3VMError("The GNS3 VM: {} must have a host only interface configured in order to start".format(self.vmname))

        vboxnet = yield from self._look_for_vboxnet(hostonly_interface_number)
        if vboxnet is None:
            raise GNS3VMError("VirtualBox host-only network could not be found for interface {} on GNS3 VM".format(hostonly_interface_number))

        if not (yield from self._check_dhcp_server(vboxnet)):
            raise GNS3VMError("DHCP must be enabled on VirtualBox host-only network: {} for GNS3 VM".format(vboxnet))

        vm_state = yield from self._get_state()
        log.info('"{}" state is {}'.format(self._vmname, vm_state))

        if vm_state == "poweroff":
            yield from self.set_vcpus(self.vcpus)
            yield from self.set_ram(self.ram)

        if vm_state in ("poweroff", "saved"):
            # start the VM if it is not running
            args = [self._vmname]
            if self._headless:
                args.extend(["--type", "headless"])
            yield from self._execute("startvm", args)
        elif vm_state == "paused":
            args = [self._vmname, "resume"]
            yield from self._execute("controlvm", args)
        ip_address = "127.0.0.1"
        try:
            # get a random port on localhost
            with socket.socket() as s:
                s.bind((ip_address, 0))
                api_port = s.getsockname()[1]
        except OSError as e:
            raise GNS3VMError("Error while getting random port: {}".format(e))

        if (yield from self._check_vbox_port_forwarding()):
            # delete the GNS3VM NAT port forwarding rule if it exists
            log.info("Removing GNS3VM NAT port forwarding rule from interface {}".format(nat_interface_number))
            yield from self._execute("controlvm", [self._vmname, "natpf{}".format(nat_interface_number), "delete", "GNS3VM"])

        # add a GNS3VM NAT port forwarding rule to redirect 127.0.0.1 with random port to port 3080 in the VM
        log.info("Adding GNS3VM NAT port forwarding rule with port {} to interface {}".format(api_port, nat_interface_number))
        yield from self._execute("controlvm", [self._vmname, "natpf{}".format(nat_interface_number),
                                               "GNS3VM,tcp,{},{},,3080".format(ip_address, api_port)])

        self.ip_address = yield from self._get_ip(hostonly_interface_number, api_port)
        self.port = 3080
        log.info("GNS3 VM has been started with IP {}".format(self.ip_address))
        self.running = True