class_docstr: Torch version of FastModel (tf).
class_docstr_tok: ["Torch","version","of","FastModel","(","tf",")","."]
code: def value_function(self):
      assert self._output is not None, "must call forward first!"
      return torch.reshape(torch.mean(self._output, -1), [-1])
  
file_path: ray/rllib/examples/models/fast_model.py
imports: from ray.rllib.models.modelv2 import ModelV2
  from ray.rllib.models.tf.tf_modelv2 import TFModelV2
  from ray.rllib.models.torch.misc import SlimFC
  from ray.rllib.models.torch.torch_modelv2 import TorchModelV2
  from ray.rllib.utils.annotations import override
  from ray.rllib.utils.framework import try_import_tf, try_import_torch
label_desc: Use image node_id 3 for calling the TorchFastModel obj's underlying member method code with example usage: obj.value_function() and returns: torch