code: def test_model_main_input_name(self):
      model_signature = inspect.signature(
          getattr(TrajectoryTransformerModel, "forward")
      )
      # The main input is the name of the argument after `self`
      observed_main_input_name = list(
          model_signature.parameters.keys()
      )[1]
      self.assertEqual(
          TrajectoryTransformerModel.main_input_name,
          observed_main_input_name,
      )
  
imports: import inspect
  import unittest
  import numpy
  from transformers import TrajectoryTransformerConfig, is_torch_available
  from transformers.testing_utils import require_torch, slow, torch_device
  from ...generation.test_generation_utils import GenerationTesterMixin
  from ...test_configuration_common import ConfigTester
  from ...test_modeling_common import ModelTesterMixin, _config_zero_init, random_attention_mask
label_desc: Use image node_id 6 for calling the TrajectoryTransformerModelTest obj's underlying member method code with example usage: obj.test_model_main_input_name() without return types