Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
2 Link Monsters Gains ATK equal to the combined Link Ratings of the monsters used for its Link Summon x 300. Unaffected by monster effects, except Link Monsters' effects, and cannot be destroyed by battle, except by battle with a Link Monster.
--ダブルバイト・ドラゴン
--Doublebyte Dragon
--
local s,id=GetID()
function s.initial_effect(c)
	--link summon
	c:EnableReviveLimit()
	Link.AddProcedure(c,aux.FilterBoolFunctionEx(Card.IsType,TYPE_LINK),2,2)
	--atkup
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_SINGLE+EFFECT_TYPE_CONTINUOUS)
	e1:SetProperty(EFFECT_FLAG_CANNOT_DISABLE)
	e1:SetCode(EVENT_SPSUMMON_SUCCESS)
	e1:SetCondition(s.atkcon)
	e1:SetOperation(s.atkop)
	c:RegisterEffect(e1)
	--immune
	local e2=Effect.CreateEffect(c)
	e2:SetType(EFFECT_TYPE_SINGLE)
	e2:SetProperty(EFFECT_FLAG_SINGLE_RANGE)
	e2:SetRange(LOCATION_MZONE)
	e2:SetCode(EFFECT_IMMUNE_EFFECT)
	e2:SetValue(s.efilter)
	c:RegisterEffect(e2)
	--indes
	local e3=Effect.CreateEffect(c)
	e3:SetType(EFFECT_TYPE_SINGLE)
	e3:SetCode(EFFECT_INDESTRUCTABLE_BATTLE)
	e3:SetValue(s.indval)
	c:RegisterEffect(e3)
end
function s.atkcon(e,tp,eg,ep,ev,re,r,rp)
	return e:GetHandler():IsLinkSummoned()
end
function s.atkop(e,tp,eg,ep,ev,re,r,rp)
	local c=e:GetHandler()
	local g=c:GetMaterial()
	local atk=0
	local tc=g:GetFirst()
	for tc in aux.Next(g) do
		local lk=tc:GetLink()
		atk=atk+lk
	end
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_SINGLE)
	e1:SetCode(EFFECT_UPDATE_ATTACK)
	e1:SetValue(atk*300)
	e1:SetReset(RESET_EVENT|RESETS_STANDARD_DISABLE)
	c:RegisterEffect(e1)
end
function s.efilter(e,te)
	return te:IsMonsterEffect() and te:GetOwner()~=e:GetOwner() and not te:IsActiveType(TYPE_LINK)
end
function s.indval(e,c)
	return not c:IsLinkMonster()
end