When I go through my dataloader, I find NoneType objects!

I would like to return the following dict type data from DataLoader.

    def __getitem__(self, index):
        tmp_data = self.benchmark[index]

        return {"id": tmp_data["id"],
                "question": tmp_data["question"],
                "options": tmp_data["options"],
                "answer": tmp_data["answer"],
                "image": tmp_data["image"],
                "question_type": tmp_data["question_type"],
                "index2ans": tmp_data["index2ans"],
                "correct_choice": tmp_data["correct_choice"],
                "all_choices": tmp_data["all_choices"],
                "empty_prompt": tmp_data["empty_prompt"],
                "final_input_prompt": tmp_data["final_input_prompt"],
                "gt_content": tmp_data["gt_content"]}

However, If I implement the loader, this returns None type data.
When I tried to print the return values of getitem, correct values were outputted…