code: def main(cmd=None):
      r"""S2T training.
  
      Example:
  
          % python s2t_train.py s2t --print_config --optim adadelta \
                  > conf/train_s2t.yaml
          % python s2t_train.py --config conf/train_s2t.yaml
      """
      S2TTask.main(cmd=cmd)
  
label_desc: Use image node_id 2 for calling a global function with example usage: main(cmd) without return types