code: def _add_ctc_loss(pred, seq_len, num_label, loss_type):
      
      label = mx.sym.Variable('label')
      if loss_type == 'warpctc':
          print("Using WarpCTC Loss")
          sm = _add_warp_ctc_loss(pred, seq_len, num_label, label)
      else:
          print("Using MXNet CTC Loss")
          assert loss_type == 'ctc'
          sm = _add_mxnet_ctc_loss(pred, seq_len, label)
      return sm
docs: Adds CTC loss on top of pred symbol and returns the resulting symbol