Appending function properly

[Benalish]

First I defined the `AppendScript` function

local mt = {
            AppendScript = function(self, handler, method)
                local func = self:GetScript(handler)
                self:SetScript(handler, function(...)
                    func(...)
                    method()
                end)
            end,
        }
        
    setmetatable(object, { __index = setmetatable(mt, getmetatable(object)) })

This way I can write

local method = function() 
                       --do stuffs 
                   end
    object:AppendScript(handler, method)

for append method to the handler script that, for example, I defined previously.

I would like to make sure that the function is not appended indefinitely: in a nutshell that the function is not appended every time the event fires.

it was recommended to make the Function Constructor in Metamethod __newindex and decide in AppendScript if it has to be recreated/destroyed, but I'm still a bit inexperienced with metatables.

Can you help me?