code: def __len__(self):
      return len(self.annotation)
  
file_path: lavis/lavis/datasets/datasets/base_dataset.py
imports: import json
  from typing import Iterable
  import pandas
  import torch
  from torch.utils.data import Dataset, ConcatDataset
  from torch.utils.data.dataloader import default_collate
label_desc: Use image node_id 2 for calling the BaseDataset obj's underlying member method code with example usage: obj.__len__() and returns: len