Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
When an opponent's monster declares an attack: Target 1 Level 4 or lower monster in your Graveyard; Special Summon it in Defense Position. It cannot be destroyed by battle or card effects this turn.
--ピンポイント・ガード
--Pinpoint Guard
local s,id=GetID()
function s.initial_effect(c)
	--When opponent's monster declares an attack, special summon 1 level 4 or lower monster from GY
	local e1=Effect.CreateEffect(c)
	e1:SetCategory(CATEGORY_SPECIAL_SUMMON)
	e1:SetProperty(EFFECT_FLAG_CARD_TARGET)
	e1:SetType(EFFECT_TYPE_ACTIVATE)
	e1:SetCode(EVENT_ATTACK_ANNOUNCE)
	e1:SetCondition(s.condition)
	e1:SetTarget(s.target)
	e1:SetOperation(s.operation)
	c:RegisterEffect(e1)
end
function s.condition(e,tp,eg,ep,ev,re,r,rp)
	return Duel.IsTurnPlayer(1-tp)
end
function s.filter(c,e,tp)
	return c:IsLevelBelow(4) and c:IsCanBeSpecialSummoned(e,0,tp,false,false,POS_FACEUP_DEFENSE)
end
function s.target(e,tp,eg,ep,ev,re,r,rp,chk,chkc)
	if chkc then return chkc:IsLocation(LOCATION_GRAVE) and chkc:IsControler(tp) and s.filter(chkc,e,tp) end
	if chk==0 then return Duel.GetLocationCount(tp,LOCATION_MZONE)>0
		and Duel.IsExistingTarget(s.filter,tp,LOCATION_GRAVE,0,1,nil,e,tp) end
	Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_SPSUMMON)
	local g=Duel.SelectTarget(tp,s.filter,tp,LOCATION_GRAVE,0,1,1,nil,e,tp)
	Duel.SetOperationInfo(0,CATEGORY_SPECIAL_SUMMON,g,1,0,0)
end
function s.operation(e,tp,eg,ep,ev,re,r,rp)
	local tc=Duel.GetFirstTarget()
	if tc:IsRelateToEffect(e) and Duel.SpecialSummon(tc,0,tp,tp,false,false,POS_FACEUP_DEFENSE)~=0 then
		--Cannot be destroyed by battle or card effects
		local e1=Effect.CreateEffect(e:GetHandler())
		e1:SetDescription(3008)
		e1:SetProperty(EFFECT_FLAG_CLIENT_HINT)
		e1:SetType(EFFECT_TYPE_SINGLE)
		e1:SetCode(EFFECT_INDESTRUCTABLE_BATTLE)
		e1:SetValue(1)
		e1:SetReset(RESETS_STANDARD_PHASE_END)
		tc:RegisterEffect(e1)
		local e2=e1:Clone()
		e2:SetCode(EFFECT_INDESTRUCTABLE_EFFECT)
		tc:RegisterEffect(e2)
	end
end