Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
Once per turn: You can discard 1 card, then activate 1 of these effects; ● Add 1 Level 4 or lower "Dragunity" monster from your Deck to your hand. ● Send 1 Dragon monster from your Deck to the GY.
--竜の渓谷
--Dragon Ravine
local s,id=GetID()
function s.initial_effect(c)
	--Activate
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_ACTIVATE)
	e1:SetCode(EVENT_FREE_CHAIN)
	c:RegisterEffect(e1)
	--Activate 1 of these effects
	local e2=Effect.CreateEffect(c)
	e2:SetDescription(aux.Stringid(id,0))
	e2:SetType(EFFECT_TYPE_IGNITION)
	e2:SetRange(LOCATION_FZONE)
	e2:SetCountLimit(1)
	e2:SetCost(s.effcost)
	e2:SetTarget(s.efftg)
	e2:SetOperation(s.effop)
	c:RegisterEffect(e2)
end
s.listed_series={SET_DRAGUNITY}
function s.effcost(e,tp,eg,ep,ev,re,r,rp,chk)
	if chk==0 then return Duel.IsExistingMatchingCard(Card.IsDiscardable,tp,LOCATION_HAND,0,1,nil) end
	Duel.DiscardHand(tp,Card.IsDiscardable,1,1,REASON_COST|REASON_DISCARD)
end
function s.thfilter(c)
	return c:IsLevelBelow(4) and c:IsSetCard(SET_DRAGUNITY) and c:IsAbleToHand()
end
function s.tgfilter(c)
	return c:IsRace(RACE_DRAGON) and c:IsAbleToGrave()
end
function s.efftg(e,tp,eg,ep,ev,re,r,rp,chk)
	local b1=Duel.IsExistingMatchingCard(s.thfilter,tp,LOCATION_DECK,0,1,nil)
	local b2=Duel.IsExistingMatchingCard(s.tgfilter,tp,LOCATION_DECK,0,1,nil)
	if chk==0 then return b1 or b2 end
	local op=Duel.SelectEffect(tp,
		{b1,aux.Stringid(id,1)},
		{b2,aux.Stringid(id,2)})
	e:SetLabel(op)
	if op==1 then
		e:SetCategory(CATEGORY_TOHAND+CATEGORY_SEARCH)
		Duel.SetOperationInfo(0,CATEGORY_TOHAND,nil,1,tp,LOCATION_DECK)
	elseif op==2 then
		e:SetCategory(CATEGORY_TOGRAVE)
		Duel.SetOperationInfo(0,CATEGORY_TOGRAVE,nil,1,tp,LOCATION_DECK)
	end
end
function s.effop(e,tp,eg,ep,ev,re,r,rp)
	local op=e:GetLabel()
	if op==1 then
		--Search 1 Level 4 or lower "Dragunity" monster
		Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_ATOHAND)
		local g=Duel.SelectMatchingCard(tp,s.thfilter,tp,LOCATION_DECK,0,1,1,nil)
		if #g>0 then
			Duel.SendtoHand(g,nil,REASON_EFFECT)
			Duel.ConfirmCards(1-tp,g)
		end
	elseif op==2 then
		--Send 1 Dragon monster from your Deck to the GY
		Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_TOGRAVE)
		local g=Duel.SelectMatchingCard(tp,s.tgfilter,tp,LOCATION_DECK,0,1,1,nil)
		if #g>0 then
			Duel.SendtoGrave(g,REASON_EFFECT)
		end
	end
end