Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
Once per turn, you can either: Target 1 face-up monster you control; equip this card to that target, OR: Unequip this card and Special Summon it. If the equipped monster would be destroyed by battle or card effect, destroy this card instead. While this card is equipped to a monster: You can banish this Equip Card; equip 1 Level 4 or lower appropriate Union monster from your Deck to the monster this card was equipped to. You can only use this effect of "Union Driver" once per turn.
--ユニオン・ドライバー
--Union Driver
--Scripted by Eerie Code
local s,id=GetID()
function s.initial_effect(c)
	--Union procedure
	aux.AddUnionProcedure(c)
	--Equip 1 appropriate Union monster from your Deck
	local e1=Effect.CreateEffect(c)
	e1:SetDescription(aux.Stringid(id,0))
	e1:SetCategory(CATEGORY_EQUIP)
	e1:SetType(EFFECT_TYPE_IGNITION)
	e1:SetRange(LOCATION_SZONE)
	e1:SetCountLimit(1,id)
	e1:SetCondition(function(e) return e:GetHandler():GetEquipTarget() end)
	e1:SetCost(s.eqcost)
	e1:SetTarget(s.eqtg)
	e1:SetOperation(s.eqop)
	c:RegisterEffect(e1)
end
function s.eqcost(e,tp,eg,ep,ev,re,r,rp,chk)
	local c=e:GetHandler()
	if chk==0 then return c:IsAbleToRemoveAsCost() end
	e:SetLabelObject(c:GetEquipTarget())
	Duel.Remove(c,POS_FACEUP,REASON_COST)
end
function s.eqfilter(c,ec,ign_ct)
	return c:IsLevelBelow(4) and c:IsType(TYPE_UNION) and c:CheckUnionTarget(ec) and aux.CheckUnionEquip(c,ec,ign_ct)
end
function s.eqtg(e,tp,eg,ep,ev,re,r,rp,chk)
	if chk==0 then return Duel.IsExistingMatchingCard(s.eqfilter,tp,LOCATION_DECK,0,1,nil,e:GetHandler():GetEquipTarget(),1) end
	e:GetLabelObject():CreateEffectRelation(e)
end
function s.eqop(e,tp,eg,ep,ev,re,r,rp)
	local tc=e:GetLabelObject()
	if tc:IsRelateToEffect(e) and tc:IsFaceup() and Duel.GetLocationCount(tp,LOCATION_SZONE)>0 then
		Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_EQUIP)
		local ec=Duel.SelectMatchingCard(tp,s.eqfilter,tp,LOCATION_DECK,0,1,1,nil,tc,0):GetFirst()
		if ec and aux.CheckUnionEquip(ec,tc) and Duel.Equip(tp,ec,tc) then
			aux.SetUnionState(ec)
		end
	end
end