Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
At the start of the Damage Step, if this card attacks a face-down Defense Position monster: Destroy that face-down monster.
--一刀両断侍
--Sasuke Samurai
local s,id=GetID()
function s.initial_effect(c)
	--destroy
	local e1=Effect.CreateEffect(c)
	e1:SetDescription(aux.Stringid(id,0))
	e1:SetCategory(CATEGORY_DESTROY)
	e1:SetType(EFFECT_TYPE_SINGLE+EFFECT_TYPE_TRIGGER_F)
	e1:SetCode(EVENT_BATTLE_START)
	e1:SetCondition(s.descon)
	e1:SetTarget(s.destg)
	e1:SetOperation(s.desop)
	c:RegisterEffect(e1)
end
function s.descon(e,tp,eg,ep,ev,re,r,rp)
	local d=Duel.GetAttackTarget()
	return e:GetHandler()==Duel.GetAttacker() and d and d:IsFacedown() and d:IsDefensePos()
end
function s.destg(e,tp,eg,ep,ev,re,r,rp,chk)
	if chk==0 then return true end
	Duel.SetOperationInfo(0,CATEGORY_DESTROY,Duel.GetAttackTarget(),1,0,0)
end
function s.desop(e,tp,eg,ep,ev,re,r,rp)
	local d=Duel.GetAttackTarget()
	if d:IsRelateToBattle() then
		Duel.Destroy(d,REASON_EFFECT)
	end
end