Minetest - Immortal effect

playereffects.register_effect_type("immortal_effect", "Immortal", "immortal.png", {"immortal"},

function(user)
    if user and user:is_player() then
        local groups = user:get_armor_groups()
        print('pre-set   ' ..dump(groups))

        playereffects.preset = groups
        user:set_armor_groups({immortal=1})
        print('post-set   ' ..dump(user:get_armor_groups()))
    end
end,

function(effect, user)
    if user and user:is_player() then
        local groups = user:get_armor_groups()
        print('pre-retract   ' ..dump(groups))

        if groups.immortal then
            user:set_armor_groups(playereffects.preset)
        end
        print('post-retract   ' ..dump(user:get_armor_groups()))
    end
end
)

minetest.register_chatcommand("morto", {
    params = "",
    description = "Immortal for 20 secs.",
    privs = {},
    func = function(name, param)
        local ret = playereffects.apply_effect_type("immortal_effect", 20, minetest.get_player_by_name(name))
        notify(name, ret)
    end,
})