class_docstr: Vissl Dataset Base class. Used to create common interface among
  base datasets. e.g. GenericSSLDataset
docstr: Number of samples.
code: def num_samples(self):
      """
      Number of samples.
      """
      ...
  
file_path: vissl/vissl/data/vissl_dataset_base.py
imports: import abc
  from typing import Callable, Dict, Set
  import torch
  from vissl.config import AttrDict
label_desc: Use image node_id 2 for calling the VisslDatasetBase obj's underlying member method code with example usage: obj.num_samples() without return types