def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def _read_img(self, file_name):
        img = Image.open(file_name)
        if img.mode != "RGB":
            img = img.convert("RGB")
        return img