code: def forward(
      self,
      feature_maps: List[Tensor],
      output_size: Union[Tuple[int, int], torch.Size, None] = None,
  ) -> Union[
      Tensor, Tuple[Tensor, ...], List[Tensor], Mapping[str, Tensor]
  ]:
      ...
  
imports: import dataclasses
  from abc import abstractmethod
  from typing import Protocol, Tuple, List, Union, Mapping, Callable
  import numpy
  import torch.jit
  from torch import nn, Tensor
  from pytorch_toolbelt.utils import pytorch_toolbelt_deprecated
label_desc: Use image node_id 2 for calling the AbstractHead obj's underlying member method code with example usage: obj.forward(feature_maps, output_size) without return types