Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
Unless your opponent sends 1 card from the top of his/her Deck to the Graveyard, he/she cannot declare an attack.
--墓守の使い魔
--Gravekeeper's Servant
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)
	--attack cost
	local e2=Effect.CreateEffect(c)
	e2:SetType(EFFECT_TYPE_FIELD)
	e2:SetCode(EFFECT_ATTACK_COST)
	e2:SetRange(LOCATION_SZONE)
	e2:SetProperty(EFFECT_FLAG_PLAYER_TARGET)
	e2:SetTargetRange(0,1)
	e2:SetCost(s.atcost)
	e2:SetOperation(s.atop)
	c:RegisterEffect(e2)
	--accumulate
	local e3=Effect.CreateEffect(c)
	e3:SetType(EFFECT_TYPE_FIELD)
	e3:SetCode(id)
	e3:SetRange(LOCATION_SZONE)
	e3:SetProperty(EFFECT_FLAG_PLAYER_TARGET)
	e3:SetTargetRange(0,1)
	c:RegisterEffect(e3)
end
function s.atcost(e,c,tp)
	local ct=#{Duel.GetPlayerEffect(tp,id)}
	return Duel.IsPlayerCanDiscardDeckAsCost(tp,ct)
end
function s.atop(e,tp,eg,ep,ev,re,r,rp)
	if Duel.IsAttackCostPaid()~=2 and e:GetHandler():IsLocation(LOCATION_SZONE) then
		Duel.DiscardDeck(tp,1,REASON_COST)
		Duel.AttackCostPaid()
	end
end