code: def __len__(self) -> int:
      return self.num_samples
  
imports: import logging
  import random
  from collections import defaultdict
  from typing import Dict
  import torch
  from torch.utils.data.sampler import Sampler
label_desc: Use image node_id 2 for calling the FlairSampler obj's underlying member method code with example usage: obj.__len__() and returns: self