Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
Target up to 2 Level 4 or lower FIRE monsters with different names in your GY; add them to your hand. You can only activate 1 "Oil" per turn.
--石油採掘
--Oil
--scripted by Naim
local s,id=GetID()
function s.initial_effect(c)
	--Add up to 2 level 4 or lower FIRE monsters to the hand
	local e1=Effect.CreateEffect(c)
	e1:SetDescription(aux.Stringid(id,0))
	e1:SetCategory(CATEGORY_TOHAND)
	e1:SetType(EFFECT_TYPE_ACTIVATE)
	e1:SetProperty(EFFECT_FLAG_CARD_TARGET)
	e1:SetCode(EVENT_FREE_CHAIN)
	e1:SetCountLimit(1,id,EFFECT_COUNT_CODE_OATH)
	e1:SetTarget(s.thtg)
	e1:SetOperation(s.thop)
	c:RegisterEffect(e1)
end
function s.thfilter(c,e)
	return c:IsLevelBelow(4) and c:IsAttribute(ATTRIBUTE_FIRE) and c:IsAbleToHand() and c:IsCanBeEffectTarget(e)
end
function s.thtg(e,tp,eg,ep,ev,re,r,rp,chk,chkc)
	if chkc then return chkc:IsControler(tp) and chkc:IsLocation(LOCATION_GRAVE) and s.thfilter(chkc,e) end
	local g=Duel.GetMatchingGroup(s.thfilter,tp,LOCATION_GRAVE,0,nil,e)
	if chk==0 then return #g>0 end
	local tg=aux.SelectUnselectGroup(g,e,tp,1,2,aux.dncheck,1,tp,HINTMSG_ATOHAND)
	Duel.SetTargetCard(tg)
	Duel.SetOperationInfo(0,CATEGORY_TOHAND,tg,#tg,tp,0)
end
function s.thop(e,tp,eg,ep,ev,re,r,rp)
	local g=Duel.GetTargetCards(e)
	if #g>0 then
		Duel.SendtoHand(g,nil,REASON_EFFECT)
	end
end