Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
This card cannot be Special Summoned. Once per turn, select 1 face-up Reptile-Type "Worm" monster on the field and change it to face-down Defense Position.
--ワーム・イーロキン
--Worm Erokin
local s,id=GetID()
function s.initial_effect(c)
	--cannot special summon
	local e1=Effect.CreateEffect(c)
	e1:SetProperty(EFFECT_FLAG_CANNOT_DISABLE+EFFECT_FLAG_UNCOPYABLE)
	e1:SetType(EFFECT_TYPE_SINGLE)
	e1:SetCode(EFFECT_SPSUMMON_CONDITION)
	c:RegisterEffect(e1)
	--position
	local e2=Effect.CreateEffect(c)
	e2:SetDescription(aux.Stringid(id,0))
	e2:SetType(EFFECT_TYPE_IGNITION)
	e2:SetCategory(CATEGORY_POSITION)
	e2:SetRange(LOCATION_MZONE)
	e2:SetCountLimit(1)
	e2:SetProperty(EFFECT_FLAG_CARD_TARGET)
	e2:SetTarget(s.postg)
	e2:SetOperation(s.posop)
	c:RegisterEffect(e2)
end
s.listed_series={SET_WORM}
function s.filter(c)
	return c:IsFaceup() and c:IsSetCard(SET_WORM) and c:IsRace(RACE_REPTILE) and c:IsCanTurnSet()
end
function s.postg(e,tp,eg,ep,ev,re,r,rp,chk,chkc)
	if chkc then return chkc:IsLocation(LOCATION_MZONE) and chkc:IsControler(tp) and s.filter(chkc) end
	if chk==0 then return Duel.IsExistingTarget(s.filter,tp,LOCATION_MZONE,0,1,nil) end
	Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_POSCHANGE)
	local g=Duel.SelectTarget(tp,s.filter,tp,LOCATION_MZONE,0,1,1,nil)
	Duel.SetOperationInfo(0,CATEGORY_POSITION,g,1,0,0)
end
function s.posop(e,tp,eg,ep,ev,re,r,rp)
	local tc=Duel.GetFirstTarget()
	if tc and tc:IsFaceup() and tc:IsRelateToEffect(e) then
		Duel.ChangePosition(tc,POS_FACEDOWN_DEFENSE,0,POS_FACEDOWN_DEFENSE,0)
	end
end