code: def __iter__(self):
      batch = []
      for idx in self.sampler:
          batch.append(idx)
          if len(batch) == self.batch_size:
              yield batch
              batch = []
      if len(batch) > 0 and not self.drop_last:
          yield batch
  
file_path: fastNLP/tests/helpers/datasets/normal_data.py
imports: import numpy
  import random
label_desc: Use image node_id 2 for calling the NormalBatchSampler obj's underlying member method code with example usage: obj.__iter__() without return types