Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
Equip only to a "Gladiator Beast" monster. It gains 300 ATK. When the equipped monster is returned from your side of the field to the Deck and this card is sent to the Graveyard, return this card to your hand.
--剣闘獣の闘器グラディウス
--Gladiator Beast's Battle Gladius
local s,id=GetID()
function s.initial_effect(c)
	aux.AddEquipProcedure(c,nil,aux.FilterBoolFunction(Card.IsSetCard,SET_GLADIATOR))
	--Increase ATK
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_EQUIP)
	e1:SetCode(EFFECT_UPDATE_ATTACK)
	e1:SetValue(300)
	c:RegisterEffect(e1)
	--Return this card to the hand
	local e2=Effect.CreateEffect(c)
	e2:SetDescription(aux.Stringid(id,0))
	e2:SetCategory(CATEGORY_TOHAND)
	e2:SetType(EFFECT_TYPE_SINGLE+EFFECT_TYPE_TRIGGER_F)
	e2:SetCode(EVENT_TO_GRAVE)
	e2:SetCondition(s.retcon)
	e2:SetTarget(s.rettg)
	e2:SetOperation(s.retop)
	c:RegisterEffect(e2)
end
s.listed_series={SET_GLADIATOR}
function s.retcon(e,tp,eg,ep,ev,re,r,rp)
	local c=e:GetHandler()
	local ec=c:GetPreviousEquipTarget()
	return c:IsReason(REASON_LOST_TARGET) and ec
		and ec:IsLocation(LOCATION_DECK|LOCATION_EXTRA)
end
function s.rettg(e,tp,eg,ep,ev,re,r,rp,chk)
	if chk==0 then return e:GetHandler():IsAbleToHand() end
	Duel.SetOperationInfo(0,CATEGORY_TOHAND,e:GetHandler(),1,0,0)
end
function s.retop(e,tp,eg,ep,ev,re,r,rp)
	local c=e:GetHandler()
	if c:IsRelateToEffect(e) then
		Duel.SendtoHand(c,nil,REASON_EFFECT)
		Duel.ConfirmCards(1-tp,c)
	end
end