Call metatable methods inside metatable itself

Question

Is there a way to call metatable methods inside the metatable itself? For example

local t = {}
local mt = {
    __index = {
        dog = function() print("bark") end,
        sound = function() t:dog() end
 }
}

setmetatable(t,mt)

t:Sound()

raises this error:

attempt to call method 'Sound' (a nil value)

Answer 1

because you don't have Sound. Only sound.