Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
Equip only to a DARK monster. It gains 400 ATK. When the equipped monster is Tributed and this card is sent to the Graveyard, return this card to your hand.
--サクリファイス・ソード
--Sword of Dark Rites
local s,id=GetID()
function s.initial_effect(c)
	aux.AddEquipProcedure(c,nil,aux.FilterBoolFunction(Card.IsAttribute,ATTRIBUTE_DARK))
	--Atk update
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_EQUIP)
	e1:SetCode(EFFECT_UPDATE_ATTACK)
	e1:SetValue(400)
	c:RegisterEffect(e1)
	--tohand
	local e2=Effect.CreateEffect(c)
	e2:SetType(EFFECT_TYPE_SINGLE+EFFECT_TYPE_TRIGGER_F)
	e2:SetCategory(CATEGORY_TOHAND)
	e2:SetDescription(aux.Stringid(id,0))
	e2:SetCode(EVENT_TO_GRAVE)
	e2:SetCondition(s.retcon)
	e2:SetTarget(s.rettg)
	e2:SetOperation(s.retop)
	c:RegisterEffect(e2)
end
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:IsReason(REASON_RELEASE)
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