code: def hybrid_forward(self, F, x):
      feat1 = self.upsample(F, self.conv1(self.pool(F, x, 1)))
      feat2 = self.upsample(F, self.conv2(self.pool(F, x, 2)))
      feat3 = self.upsample(F, self.conv3(self.pool(F, x, 3)))
      feat4 = self.upsample(F, self.conv4(self.pool(F, x, 6)))
      x = F.concat(x, feat1, feat2, feat3, feat4, dim=1)
      x = self.out(x)
      return x
  
imports: from mxnet.context import cpu
  from mxnet.gluon.block import HybridBlock
  from mxnet.gluon import nn
label_desc: Use image node_id 4 for calling the _FastPyramidPooling obj's underlying member method code with example usage: obj.hybrid_forward(F, x) and returns: x