Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
Discard 1 card. Special Summon 1 Level 4 or lower monster from your opponent's Graveyard to your side of the field, and your opponent Special Summons 1 Level 4 or lower monster from your Graveyard to your opponent's side of the field. Those monsters are destroyed during the End Phase of the next turn.
--ボーン・テンプル・ブロック
--Bone Temple Block
local s,id=GetID()
function s.initial_effect(c)
	--Activate
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_ACTIVATE)
	e1:SetCategory(CATEGORY_SPECIAL_SUMMON)
	e1:SetCode(EVENT_FREE_CHAIN)
	e1:SetProperty(EFFECT_FLAG_CARD_TARGET)
	e1:SetTarget(s.target)
	e1:SetOperation(s.operation)
	c:RegisterEffect(e1)
end
function s.filter(c,e,tp)
	return c:IsLevelBelow(4) and c:IsCanBeSpecialSummoned(e,0,tp,false,false)
end
function s.target(e,tp,eg,ep,ev,re,r,rp,chk,chkc)
	if chkc then return false end
	if chk==0 then
		return Duel.GetFieldGroupCount(tp,LOCATION_HAND,0)~=0
			and Duel.IsExistingTarget(s.filter,tp,0,LOCATION_GRAVE,1,nil,e,tp)
			and Duel.GetLocationCount(tp,LOCATION_MZONE)>0
			and Duel.IsExistingTarget(s.filter,1-tp,0,LOCATION_GRAVE,1,nil,e,1-tp)
			and Duel.GetLocationCount(1-tp,LOCATION_MZONE)>0
	end
	Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_SPSUMMON)
	local sg=Duel.SelectTarget(tp,s.filter,tp,0,LOCATION_GRAVE,1,1,nil,e,tp)
	Duel.Hint(HINT_SELECTMSG,1-tp,HINTMSG_SPSUMMON)
	local og=Duel.SelectTarget(1-tp,s.filter,1-tp,0,LOCATION_GRAVE,1,1,nil,e,1-tp)
	local sc=sg:GetFirst()
	local oc=og:GetFirst()
	local g=Group.FromCards(sc,oc)
	Duel.SetOperationInfo(0,CATEGORY_SPECIAL_SUMMON,g,2,PLAYER_ALL,1-g:GetFirst():GetOwner())
	e:SetLabelObject(sc)
end
function s.operation(e,tp,eg,ep,ev,re,r,rp)
	if Duel.DiscardHand(tp,Card.IsDiscardable,1,1,REASON_EFFECT|REASON_DISCARD)==0 then return end
	local sc=e:GetLabelObject()
	local g=Duel.GetChainInfo(0,CHAININFO_TARGET_CARDS)
	local oc=g:GetFirst()
	if oc==sc then oc=g:GetNext() end
	if sc:IsRelateToEffect(e) then
		Duel.SpecialSummonStep(sc,0,tp,tp,false,false,POS_FACEUP)
		local e1=Effect.CreateEffect(e:GetHandler())
		e1:SetType(EFFECT_TYPE_FIELD+EFFECT_TYPE_CONTINUOUS)
		e1:SetProperty(EFFECT_FLAG_IGNORE_IMMUNE)
		e1:SetRange(LOCATION_MZONE)
		e1:SetCode(EVENT_PHASE+PHASE_END)
		e1:SetCondition(s.descon)
		e1:SetOperation(s.desop)
		e1:SetReset(RESETS_STANDARD_PHASE_END,2)
		e1:SetCountLimit(1)
		e1:SetLabel(Duel.GetTurnCount())
		sc:RegisterEffect(e1,true)
	end
	if oc:IsRelateToEffect(e) then
		Duel.SpecialSummonStep(oc,0,1-tp,1-tp,false,false,POS_FACEUP)
		local e1=Effect.CreateEffect(e:GetHandler())
		e1:SetType(EFFECT_TYPE_FIELD+EFFECT_TYPE_CONTINUOUS)
		e1:SetProperty(EFFECT_FLAG_IGNORE_IMMUNE)
		e1:SetRange(LOCATION_MZONE)
		e1:SetCode(EVENT_PHASE+PHASE_END)
		e1:SetCondition(s.descon)
		e1:SetOperation(s.desop)
		e1:SetReset(RESETS_STANDARD_PHASE_END,2)
		e1:SetCountLimit(1)
		e1:SetLabel(Duel.GetTurnCount())
		oc:RegisterEffect(e1,true)
	end
	Duel.SpecialSummonComplete()
end
function s.descon(e,tp,eg,ep,ev,re,r,rp)
	return Duel.GetTurnCount()~=e:GetLabel()
end
function s.desop(e,tp,eg,ep,ev,re,r,rp)
	Duel.Destroy(e:GetHandler(),REASON_EFFECT)
end