code: def __iter__(self):
      if self.sampling_mode == "normal":
          return TrainDataSampler(self.nbatches, self.sampling)
      else:
          return TrainDataSampler(self.nbatches, self.cross_sampling)
  
imports: import os
  import ctypes
  import numpy
label_desc: Use image node_id 19 for calling the TrainDataLoader obj's underlying member method code with example usage: obj.__iter__() and returns: TrainDataSampler, TrainDataSampler