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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 devices(self):
 """ computes the name of the disk devices that are suitable installation targets by subtracting CDROM- and USB devices from the list of total mounts. """

        install_devices = self.install_devices
        if 'bootstrap-system-devices' in env.instance.config:
            devices = set(env.instance.config['bootstrap-system-devices'].split())
        else:
            devices = set(self.sysctl_devices)
            for sysctl_device in self.sysctl_devices:
                for install_device in install_devices:
                    if install_device.startswith(sysctl_device):
                        devices.remove(sysctl_device)
        return devices