code: def __len__(self):
      return len(self.groups)
  
file_path: backprop/backprop/utils/samplers.py
imports: import random
  import numpy
  from torch.utils.data.sampler import Sampler
label_desc: Use image node_id 2 for calling the SameGroupSampler obj's underlying member method code with example usage: obj.__len__() and returns: len