code: def get_output_spec(self) -> FeatureMapsSpecification:
      return self.output_spec
  
file_path: pytorch-toolbelt/pytorch_toolbelt/modules/decoders/unet.py
imports: from typing import List, Union, Type, Tuple, Mapping
  import torch
  import logging
  from torch import nn
  from pytorch_toolbelt.modules.unet import UnetBlock, UnetResidualBlock
  from pytorch_toolbelt.modules.interfaces import AbstractDecoder, FeatureMapsSpecification
  from pytorch_toolbelt.modules.upsample import AbstractResizeLayer, UpsampleLayerType, instantiate_upsample_block, DeconvolutionUpsample2d
  from pytorch_toolbelt.modules.normalization import NORM_BATCH, instantiate_normalization_block
  from pytorch_toolbelt.modules.activations import ACT_RELU
label_desc: Use image node_id 3 for calling the UNetDecoder obj's underlying member method code with example usage: obj.get_output_spec() and returns: self