      num_workers = d2l.get_dataloader_workers()
      data_dir = d2l.download_extract('wikitext-2', 'wikitext-2')
      paragraphs = _read_wiki(data_dir)
      train_set = _WikiTextDataset(paragraphs, max_len)
      train_iter = paddle.io.DataLoader(dataset=train_set, batch_size=batch_size,
                                          shuffle=True, num_workers=num_workers)
      return train_iter, train_set.vocab
  
  def _get_batch_loss_bert(net, loss, vocab_size, tokens_X,
                           segments_X, valid_lens_x,
 
</s> remove         shuffle=True, drop_last=True, num_workers=num_workers)
 </s> add         shuffle=True, return_list=True, drop_last=True, num_workers=num_workers) </s> remove         dataset, batch_size=batch_size, shuffle=True,
 </s> add         dataset, batch_size=batch_size, shuffle=True, return_list=True, </s> remove                                            batch_size=batch_size)
 </s> add                                            batch_size=batch_size, return_list=True) </s> remove         drop_last=True, num_workers=num_workers)
 </s> add         drop_last=True, return_list=True, num_workers=num_workers)
    train_iter = paddle.io.DataLoader(dataset=train_set, batch_size=batch_size, return_list=True,
      num_workers = d2l.get_dataloader_workers()
      data_dir = d2l.download_extract('wikitext-2', 'wikitext-2')
      paragraphs = _read_wiki(data_dir)
      train_set = _WikiTextDataset(paragraphs, max_len)
    train_iter = paddle.io.DataLoader(dataset=train_set, batch_size=batch_size, return_list=True,
                                          shuffle=True, num_workers=num_workers)
      return train_iter, train_set.vocab
  
  def _get_batch_loss_bert(net, loss, vocab_size, tokens_X,
                           segments_X, valid_lens_x,
keep keep keep keep replace keep keep keep keep keep
 [PaddlePaddle]Remove multi gpu training (#1205)

* Remove multi gpu training

* Try to Add return list for avoiding runtime error

* Set num_workers to 0

* Remove numbers of fcn.md

* Fix natural-language-inference-attention.md&bert-pretraining.md 
d2l/paddle.py