code: def _build_aggs(self):
      aggs = []
      for i in range(self.n_r):
          aggs.append(
              self.add_sublayer(
                  "{}".format(i),
                  nn.Sequential(
                      (
                          "conv1",
                          nn.Conv2D(
                              self.d_in,
                              self.d_middle,
                              3,
                              2,
                              1,
                              bias_attr=False,
                          ),
                      ),
                      ("bn1", nn.BatchNorm(self.d_middle)),
                      ("act", self.act),
                      (
                          "conv2",
                          nn.Conv2D(
                              self.d_middle,
                              self.d_out,
                              3,
                              2,
                              1,
                              bias_attr=False,
                          ),
                      ),
                      ("bn2", nn.BatchNorm(self.d_out)),
                  ),
              )
          )
      return aggs
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import paddle
  from paddle import nn
  import paddle.nn.functional
label_desc: Use image node_id 2 for calling the PoolAggregate obj's underlying member method code with example usage: obj._build_aggs() and returns: aggs