Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
When this card is flipped face-up: You can Special Summon any number of "Ninja" monsters, except "Senior Silver Ninja", from your hand and/or Graveyard in face-down Defense Position. There can only be 1 face-up "Senior Silver Ninja" on the field.
--渋い忍者
--Senior Silver Ninja
local s,id=GetID()
function s.initial_effect(c)
	c:SetUniqueOnField(1,1,id)
	--spsummon
	local e1=Effect.CreateEffect(c)
	e1:SetDescription(aux.Stringid(id,0))
	e1:SetType(EFFECT_TYPE_TRIGGER_O+EFFECT_TYPE_SINGLE)
	e1:SetCategory(CATEGORY_SPECIAL_SUMMON)
	e1:SetCode(EVENT_FLIP)
	e1:SetProperty(EFFECT_FLAG_DAMAGE_STEP)
	e1:SetTarget(s.sptg)
	e1:SetOperation(s.spop)
	c:RegisterEffect(e1)
end
s.listed_series={SET_NINJA}
s.listed_names={id}
function s.filter(c,e,tp)
	return c:IsSetCard(SET_NINJA) and not c:IsCode(id) and c:IsCanBeSpecialSummoned(e,0,tp,false,false,POS_FACEDOWN_DEFENSE)
end
function s.sptg(e,tp,eg,ep,ev,re,r,rp,chk)
	if chk==0 then return Duel.GetLocationCount(tp,LOCATION_MZONE)>0
		and Duel.IsExistingMatchingCard(s.filter,tp,LOCATION_HAND|LOCATION_GRAVE,0,1,nil,e,tp) end
	Duel.SetOperationInfo(0,CATEGORY_SPECIAL_SUMMON,nil,1,tp,LOCATION_HAND|LOCATION_GRAVE)
end
function s.spop(e,tp,eg,ep,ev,re,r,rp)
	local ft=Duel.GetLocationCount(tp,LOCATION_MZONE)
	if ft<=0 then return end
	Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_SPSUMMON)
	local g=Duel.SelectMatchingCard(tp,aux.NecroValleyFilter(s.filter),tp,LOCATION_HAND|LOCATION_GRAVE,0,1,ft,nil,e,tp)
	if #g>0 then
		Duel.SpecialSummon(g,0,tp,tp,false,false,POS_FACEDOWN_DEFENSE)
		Duel.ConfirmCards(1-tp,g)
	end
end