code: def __iter__(self):
      itr = self.ds.__iter__()
      for _ in range(self.__len__()):
          feats = []
          labs = []
          for _ in range(self.batch):
              feat, lab = next(itr)
              feats.append(feat)
              labs.append(lab)
          batchfeat = batch_feature(feats)
          batchlab = sparse_label(labs)
          seqlen = np.asarray([k.shape[0] for k in feats])
          yield [
              batchfeat,
              batchlab[0],
              batchlab[1],
              batchlab[2],
              seqlen,
          ]
  
file_path: tensorpack/examples/CTC-TIMIT/timitdata.py
imports: import numpy
  from tensorpack import ProxyDataFlow
label_desc: Use image node_id 3 for calling the TIMITBatch obj's underlying member method code with example usage: obj.__iter__() without return types