code: def test_forward_signature(self):
      (
          config,
          _,
      ) = self.model_tester.prepare_config_and_inputs_for_common()
  
      for model_class in self.all_model_classes:
          model = model_class(config)
          signature = inspect.signature(model.forward)
          # signature.parameters is an OrderedDict => so arg_names order is deterministic
          arg_names = [*signature.parameters.keys()]
  
          expected_arg_names = [
              "states",
              "actions",
              "rewards",
              "returns_to_go",
              "timesteps",
              "attention_mask",
          ]
  
          self.assertListEqual(
              arg_names[: len(expected_arg_names)], expected_arg_names
          )
  
imports: import inspect
  import unittest
  from transformers import DecisionTransformerConfig, is_torch_available
  from transformers.testing_utils import require_torch, slow, torch_device
  from ...generation.test_utils import GenerationTesterMixin
  from ...test_configuration_common import ConfigTester
  from ...test_modeling_common import ModelTesterMixin, floats_tensor, ids_tensor, random_attention_mask
  from ...test_pipeline_mixin import PipelineTesterMixin
label_desc: Use image node_id 5 for calling the DecisionTransformerModelTest obj's underlying member method code with example usage: obj.test_forward_signature() without return types