local meta = {}
meta.__index = meta
local T = setmetatable({}, meta) -- T is the actual table you use


T[asd] = 5 -- new change gets saved inside T


func OnSave()
    local meta = getmetatable(T)
    local keystodel = {}
    for k,v in pairs(T) do -- save the data and move it to metatable
       Save(k, v)
       meta[k] = v
       table.insert(keystodel, k)
    end
    for k,v in ipairs(keystodel) do -- not to confuse above loop saved all keys to a table and now deleting them
       T[v] = nil
    end

end