Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
At the start of the Damage Step, if this card battles a DARK monster: Destroy that monster.
--ヴァンパイア・キラー
--Vampire Hunter
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:SetTarget(s.destg)
	e1:SetOperation(s.desop)
	c:RegisterEffect(e1)
end
function s.destg(e,tp,eg,ep,ev,re,r,rp,chk)
	local c=e:GetHandler()
	local bc=c:GetBattleTarget()
	if chk==0 then return bc and bc:IsFaceup() and bc:IsAttribute(ATTRIBUTE_DARK) end
	Duel.SetOperationInfo(0,CATEGORY_DESTROY,bc,1,0,0)
end
function s.desop(e,tp,eg,ep,ev,re,r,rp)
	local c=e:GetHandler()
	local bc=c:GetBattleTarget()
	if bc:IsRelateToBattle() then
		Duel.Destroy(bc,REASON_EFFECT)
	end
end