class_docstr: Skip connection layer.
  
  Adds the original input to the output (regular residual layer) OR uses
  input as hidden state input to a given fan_in_layer.
code: def forward(self, inputs: TensorType, **kwargs) -> TensorType:
      # del kwargs
      outputs = self._layer(inputs, **kwargs)
      # Residual case, just add inputs to outputs.
      if self._fan_in_layer is None:
          outputs = outputs + inputs
      # Fan-in e.g. RNN: Call fan-in with `inputs` and `outputs`.
      else:
          # NOTE: In the GRU case, `inputs` is the state input.
          outputs = self._fan_in_layer((inputs, outputs))
  
      return outputs
  
imports: from ray.rllib.utils.framework import try_import_torch
  from ray.rllib.utils.typing import TensorType
  from typing import Optional
label_desc: Use image node_id 2 for calling the SkipConnection obj's underlying member method code with example usage: obj.forward(inputs) and returns: outputs