code: def test_fixed_noise_likelihood(self):
      for (
          iteration_fidelity,
          data_fidelities,
      ) in self.FIDELITY_TEST_PAIRS:
          for batch_shape, m, dtype, lin_trunc in itertools.product(
              (torch.Size(), torch.Size([2])),
              (1, 2),
              (torch.float, torch.double),
              (False, True),
          ):
              tkwargs = {"device": self.device, "dtype": dtype}
              model, model_kwargs = self._get_model_and_data(
                  iteration_fidelity=iteration_fidelity,
                  data_fidelities=data_fidelities,
                  batch_shape=batch_shape,
                  m=m,
                  lin_truncated=lin_trunc,
                  **tkwargs,
              )
              self.assertIsInstance(
                  model.likelihood, FixedNoiseGaussianLikelihood
              )
              self.assertTrue(
                  torch.equal(
                      model.likelihood.noise.contiguous().view(-1),
                      model_kwargs["train_Yvar"].contiguous().view(-1),
                  )
              )
  
imports: import itertools
  import warnings
  from typing import Tuple
  import torch
  from botorch.exceptions.errors import UnsupportedError
  from botorch.exceptions.warnings import OptimizationWarning
  from botorch.fit import fit_gpytorch_mll
  from botorch.models.gp_regression_fidelity import FixedNoiseMultiFidelityGP, SingleTaskMultiFidelityGP
  from botorch.models.transforms import Normalize, Standardize
  from botorch.posteriors import GPyTorchPosterior
  from botorch.sampling import SobolQMCNormalSampler
  from botorch.utils.datasets import SupervisedDataset
  from botorch.utils.testing import _get_random_data, BotorchTestCase
  from gpytorch.kernels.scale_kernel import ScaleKernel
  from gpytorch.likelihoods import FixedNoiseGaussianLikelihood
  from gpytorch.means import ConstantMean
  from gpytorch.mlls.exact_marginal_log_likelihood import ExactMarginalLogLikelihood
  from torch import Tensor
label_desc: Use image node_id 3 for calling the TestFixedNoiseMultiFidelityGP obj's underlying member method code with example usage: obj.test_fixed_noise_likelihood() without return types