code: def forward(self, x):
      if self.downsample:
          x = self.downsample(x)
      x = self.blocks(x)
      return x
  
imports: import paddle
  import paddle.nn
  import paddle.nn.functional
  from paddle.nn.initializer import KaimingNormal, Constant
  from paddle.nn import Conv2D, BatchNorm2D, ReLU, AdaptiveAvgPool2D, MaxPool2D
  from paddle.regularizer import L2Decay
  from paddle import ParamAttr
  import copy
  from ppdet.core.workspace import register, serializable
  from ..shape_spec import ShapeSpec
label_desc: Use image node_id 2 for calling the HG_Stage obj's underlying member method code with example usage: obj.forward(x) and returns: x