code: def forward(self, x):
      shrink_maps = self.binarize(x)
      threshold_maps = self.thresh(x)
      if self.training:
          binary_maps = self.step_function(shrink_maps, threshold_maps)
          y = paddle.concat(
              (shrink_maps, threshold_maps, binary_maps), axis=1
          )
      else:
          y = paddle.concat((shrink_maps, threshold_maps), axis=1)
      return y
  
file_path: PaddleOCR/benchmark/PaddleOCR_DBNet/models/head/DBHead.py
imports: import paddle
  from paddle import nn, ParamAttr
label_desc: Use image node_id 2 for calling the DBHead obj's underlying member method code with example usage: obj.forward(x) and returns: y