Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
You can Special Summon this card (from your hand). You can only Special Summon "Dynatherium" once per turn this way. If Summoned this way: Activate this effect; your opponent can Special Summon 1 Level 4 monster from either GY. * The above text is unofficial and describes the card's functionality in the OCG.
--俊足なカバ バリキテリウム
--Dynatherium
local s,id=GetID()
function s.initial_effect(c)
	--special summon
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_FIELD)
	e1:SetCode(EFFECT_SPSUMMON_PROC)
	e1:SetProperty(EFFECT_FLAG_UNCOPYABLE)
	e1:SetRange(LOCATION_HAND)
	e1:SetCountLimit(1,id,EFFECT_COUNT_CODE_OATH)
	e1:SetCondition(s.spcon)
	e1:SetValue(1)
	c:RegisterEffect(e1)
	--special summon when summoned
	local e2=Effect.CreateEffect(c)
	e2:SetDescription(aux.Stringid(id,0))
	e2:SetCategory(CATEGORY_SPECIAL_SUMMON)
	e2:SetType(EFFECT_TYPE_SINGLE+EFFECT_TYPE_TRIGGER_F)
	e2:SetCode(EVENT_SPSUMMON_SUCCESS)
	e2:SetCondition(s.condition)
	e2:SetTarget(s.target)
	e2:SetOperation(s.operation)
	c:RegisterEffect(e2)
end
function s.spcon(e,c)
	if c==nil then return true end
	local tp=c:GetControler()
	return Duel.GetLocationCount(tp,LOCATION_MZONE)>0
end
function s.condition(e,tp,eg,ep,ev,re,r,rp)
	return e:GetHandler():IsSummonType(SUMMON_TYPE_SPECIAL+1)
end
function s.target(e,tp,eg,ep,ev,re,r,rp,chk)
	if chk==0 then return true end
	Duel.SetPossibleOperationInfo(0,CATEGORY_SPECIAL_SUMMON,nil,1,PLAYER_EITHER,LOCATION_GRAVE)
end
function s.filter(c,e,tp)
	return c:IsLevel(4) and c:IsCanBeSpecialSummoned(e,0,1-tp,false,false)
end
function s.operation(e,tp,eg,ep,ev,re,r,rp)
	local g=Duel.GetMatchingGroup(aux.NecroValleyFilter(s.filter),0,LOCATION_GRAVE,LOCATION_GRAVE,nil,e,tp)
	if #g>0 and Duel.GetLocationCount(1-tp,LOCATION_MZONE)>0
		and Duel.SelectYesNo(1-tp,aux.Stringid(id,1)) then
		Duel.Hint(HINT_SELECTMSG,1-tp,HINTMSG_SPSUMMON)
		local sg=g:Select(1-tp,1,1,nil)
		Duel.SpecialSummon(sg,0,1-tp,1-tp,false,false,POS_FACEUP)
	end
end