refactor tools/export_model.lua
refactor tools/export_model.lua

Spitfire1900/upscaler,nagadomi/waifu2x,nagadomi/waifu2x,zyhkz/waifu2x,zyhkz/waifu2x,nagadomi/waifu2x,zyhkz/waifu2x,zyhkz/waifu2x,Spitfire1900/upscaler,higankanshi/waifu2x,vitaliylag/waifu2x,higankanshi/waifu2x,vitaliylag/waifu2x,vitaliylag/waifu2x,nagadomi/waifu2x,higankanshi/waifu2x,nagadomi/waifu2x