code: def forward(self, x):
      x = self.conv1(x)
      x1, x2 = x.chunk(2, axis=1)
      x1 = self.branch1(x1)
      x2 = self.expand_conv(x2)
      x2 = self.depthwise_conv(x2)
      x2 = self.linear_conv(x2)
      out = paddle.concat([x1, x2], axis=1)
      out = channel_shuffle(out, groups=2)
  
      return out
  
imports: import paddle
  import paddle.nn
  import paddle.nn.functional
  from numbers import Integral
  from paddle import ParamAttr
  from paddle.regularizer import L2Decay
  from paddle.nn.initializer import Normal, Constant
  from ppdet.core.workspace import register
  from ppdet.modeling.shape_spec import ShapeSpec
  from ppdet.modeling.ops import channel_shuffle
  from ..None import layers
label_desc: Use image node_id 2 for calling the Stem obj's underlying member method code with example usage: obj.forward(x) and returns: out