function bu(u, b)
	local i = 1
	while (UnitBuff(u, i)) do
		if (string.find(UnitBuff(u, i), b)) then
			return true
		end
	i = i + 1
	end
	return false
end

if bu("Pet","Lesser Invisibility") then
	UseContainerItem(0, 1)
else
	CastPetAction(7)
	UseContainerItem(0, 1)
end