def METHOD_NAME(self, devname):
    try:
        safe_dbus.call_sync(self.iface_prefix,
                            self.path_prefix + '/block_devices/' + devname,
                            self.iface_prefix + '.Block',
                            'Format',
                            GLib.Variant('(sa{sv})', ('empty', {'erase': GLib.Variant("s", 'zero')})))
    except Exception as e:
        self.exception = e