code: def forward(self, x):
      outs = [x]
      for pool in self.pool:
          outs.append(pool(x))
      if self.data_format == "NCHW":
          y = paddle.concat(outs, axis=1)
      else:
          y = paddle.concat(outs, axis=-1)
  
      y = self.conv(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 SPP obj's underlying member method code with example usage: obj.forward(x) and returns: y