Load a translator file

def __load_file(self, key_list) -> str:
        """ Load a translator file """
        file = str(key_list[0]) + self.extension
        key_list.pop(0)
        file_path = os.path.join(self.path, file)
        if os.path.exists(file_path):
            return Json.from_file(file_path)
        else:
            raise FileNotFoundError(file_path)