code: def test_fallback(self) -> None:
      with patch.dict(covar_module_argparse.funcs, {}):
  
          @covar_module_argparse.register(Kernel)
          def _argparse(covar_module_class: Kernel) -> None:
              pass
  
          self.assertEqual(covar_module_argparse[Kernel], _argparse)
  
imports: from __future__ import annotations
  from unittest.mock import patch
  import torch
  from ax.models.torch.botorch_modular.input_constructors.covar_modules import covar_module_argparse
  from ax.models.torch.botorch_modular.kernels import ScaleMaternKernel
  from ax.utils.common.testutils import TestCase
  from botorch.models.gp_regression import SingleTaskGP
  from botorch.models.multitask import MultiTaskGP
  from botorch.utils.datasets import SupervisedDataset
  from gpytorch.kernels.kernel import Kernel
  from gpytorch.priors import GammaPrior
label_desc: Use image node_id 4 for calling the CovarModuleArgparseTest obj's underlying member method code with example usage: obj.test_fallback() without return types