code: def test_forward(self):
      neck = FPN_UNet(self.in_channels, self.out_channels)
      neck.init_weights()
      out = neck(self.feature)
      self.assertTrue(
          out.shape
          == torch.Size([1, self.out_channels, self.s * 4, self.s * 4])
      )
  
imports: import unittest
  import torch
  from mmocr.models.textdet.necks import FPN_UNet
label_desc: Use image node_id 3 for calling the TestFPNUnet obj's underlying member method code with example usage: obj.test_forward() without return types