class_docstr: Split to two transformer header at the last layer.
  Cls_layer is used to structure token classification.
  Bbox_layer is used to regress bbox coord.
code: def forward_test(self, out_enc):
      batch_size = out_enc.shape[0]
      SOS = paddle.zeros([batch_size, 1], dtype="int64") + self.SOS
      output, bbox_output = self.greedy_forward(SOS, out_enc)
      output = F.softmax(output)
      return {"structure_probs": output, "loc_preds": bbox_output}
  
imports: import copy
  import math
  import paddle
  from paddle import nn
  from paddle.nn import functional
label_desc: Use image node_id 6 for calling the TableMasterHead obj's underlying member method code with example usage: obj.forward_test(out_enc) and returns: dict