code: def forward(self, x):
      y1 = self.conv1(x)
      y2 = self.conv2(x)
      y2 = self.convs(y2)
      y = paddle.concat([y1, y2], axis=1)
      y = self.conv3(y)
      return y
  
imports: import math
  import copy
  import numpy
  import paddle
  import paddle.nn
  import paddle.nn.functional
  from ppdet.core.workspace import register, serializable
  from ppdet.modeling.layers import DropBlock, MultiHeadAttention
  from ppdet.modeling.ops import get_act_fn
  from ..backbones.cspresnet import ConvBNLayer, BasicBlock
  from ..shape_spec import ShapeSpec
  from ..initializer import linear_init_
label_desc: Use image node_id 2 for calling the CSPStage obj's underlying member method code with example usage: obj.forward(x) and returns: y