code: def __len__(self):
      return len(self.questions)
  
imports: import argparse
  import torch
  import os
  import json
  from tqdm import tqdm
  import shortuuid
  from llamavid.constants import IMAGE_TOKEN_INDEX, DEFAULT_IMAGE_TOKEN, DEFAULT_IM_START_TOKEN, DEFAULT_IM_END_TOKEN
  from llamavid.conversation import conv_templates, SeparatorStyle
  from llamavid.model.builder import load_pretrained_model
  from llava.utils import disable_torch_init
  from llava.mm_utils import tokenizer_image_token, process_images, get_model_name_from_path
  from torch.utils.data import Dataset, DataLoader
  from PIL import Image
  import math
label_desc: Use image node_id 3 for calling the CustomDataset obj's underlying member method code with example usage: obj.__len__() and returns: len