torch.autograd.Variable(target.cuda(async=True)) ---async调用cuda()引发SyntaxError

 ./projects/personachat/persona_seq2seq.py:2220:43: E999 SyntaxError: invalid syntax

    
                 self.zs.copy_(zs, async=True)
    
                                       ^
    
 ./parlai/agents/vsepp_caption/vsepp_caption.py:160:38: E999 SyntaxError: invalid syntax
    
         images = images.cuda(async=True)
    
                                  ^
    
 ./parlai/agents/drqa/model.py:89:43: E999 SyntaxError: invalid syntax
    
         inputs = [Variable(e.cuda(async=True)) for e in ex[:5]]
    
                                       ^
    
 3     E999 SyntaxE