341     def assert_test_image_in_usb_disk(self, usb_dev=None):  argument
350         if usb_dev:
354             usb_dev = self.servo.probe_host_usb_dev()
355             if not usb_dev:
359         rootfs = '%s%s' % (usb_dev, self._ROOTFS_PARTITION_NUMBER)
360         logging.info('usb dev is %s', usb_dev)
977     def _modify_usb_kernel(self, usb_dev, from_magic, to_magic):  argument
991         kernel_part = self._join_part(usb_dev, self.KERNEL_MAP['a'])
1009     def corrupt_usb_kernel(self, usb_dev):  argument
1014         self._modify_usb_kernel(usb_dev, self.CHROMEOS_MAGIC,
1017     def restore_usb_kernel(self, usb_dev):  argument
1022         self._modify_usb_kernel(usb_dev, self.CORRUPTED_MAGIC,