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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):
 """ Starts this VirtualBox VM. """


        if self.status == "started":
            return

        # resume the VM if it is paused
        vm_state = yield from self._get_vm_state()
        if vm_state == "paused":
            yield from self.resume()
            return

        # VM must be powered off to start it
        if vm_state != "poweroff":
            raise VirtualBoxError("VirtualBox VM not powered off")

        yield from self._set_network_options()
        yield from self._set_serial_console()

        # check if there is enough RAM to run
        self.check_available_ram(self.ram)

        args = [self._vmname]
        if self._headless:
            args.extend(["--type", "headless"])
        result = yield from self.manager.execute("startvm", args)
        self.status = "started"
        log.info("VirtualBox VM '{name}' [{id}] started".format(name=self.name, id=self.id))
        log.debug("Start result: {}".format(result))

        # add a guest property to let the VM know about the GNS3 name
        yield from self.manager.execute("guestproperty", ["set", self._vmname, "NameInGNS3", self.name])
        # add a guest property to let the VM know about the GNS3 project directory
        yield from self.manager.execute("guestproperty", ["set", self._vmname, "ProjectDirInGNS3", self.working_dir])

        yield from self._start_ubridge()
        for adapter_number in range(0, self._adapters):
            nio = self._ethernet_adapters[adapter_number].get_nio(0)
            if nio:
                yield from self.add_ubridge_udp_connection("VBOX-{}-{}".format(self._id, adapter_number),
                                                           self._local_udp_tunnels[adapter_number][1],
                                                           nio)

        yield from self._start_console()

        if (yield from self.check_hw_virtualization()):
            self._hw_virtualization = True