Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
2 Level 7 monsters You can also Xyz Summon this card by using a Rank 5 or 6 Xyz Monster you control as material. (Transfer its materials to this card.) If this card attacks a Defense Position monster, inflict piercing battle damage.
--迅雷の騎士ガイアドラグーン
--Gaia Dragon, the Thunder Charger
local s,id=GetID()
function s.initial_effect(c)
	--xyz summon
	Xyz.AddProcedure(c,nil,7,2,s.ovfilter,aux.Stringid(id,0))
	c:EnableReviveLimit()
	--pierce
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_SINGLE)
	e1:SetCode(EFFECT_PIERCE)
	c:RegisterEffect(e1)
end
function s.ovfilter(c)
	local rk=c:GetRank()
	return c:IsFaceup() and (rk==5 or rk==6)
end