code: def forward(self, x):
      f = x[2:][::-1]
      h0 = self.h0_conv(f[0])
      h1 = self.h1_conv(f[1])
      h2 = self.h2_conv(f[2])
      h3 = self.h3_conv(f[3])
      h4 = self.h4_conv(f[4])
  
      g0 = self.g0_conv(h0)
      g1 = self._add_relu(g0, h1)
      g1 = self.g1_conv(g1)
      g2 = self.g2_conv(self._add_relu(g1, h2))
      g3 = self.g3_conv(self._add_relu(g2, h3))
      g4 = self.g4_conv(self._add_relu(g3, h4))
  
      return g4
  
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
  from paddle import ParamAttr
label_desc: Use image node_id 3 for calling the FPN_Up_Fusion obj's underlying member method code with example usage: obj.forward(x) and returns: g4