code: def test_initialize_lengthscale_prior(self):
      kernel = LinearTruncatedFidelityKernel(
          fidelity_dims=[1, 2], dimension=3
      )
      self.assertTrue(
          isinstance(
              kernel.covar_module_unbiased.lengthscale_prior, GammaPrior
          )
      )
      self.assertTrue(
          isinstance(
              kernel.covar_module_biased.lengthscale_prior, GammaPrior
          )
      )
      kernel2 = LinearTruncatedFidelityKernel(
          fidelity_dims=[1, 2],
          dimension=3,
          lengthscale_prior_unbiased=NormalPrior(1, 1),
      )
      self.assertTrue(
          isinstance(
              kernel2.covar_module_unbiased.lengthscale_prior,
              NormalPrior,
          )
      )
      kernel2 = LinearTruncatedFidelityKernel(
          fidelity_dims=[1, 2],
          dimension=3,
          lengthscale_prior_biased=NormalPrior(1, 1),
      )
      self.assertTrue(
          isinstance(
              kernel2.covar_module_biased.lengthscale_prior, NormalPrior
          )
      )
  
imports: import itertools
  import torch
  from botorch.exceptions import UnsupportedError
  from botorch.models.kernels.linear_truncated_fidelity import LinearTruncatedFidelityKernel
  from botorch.utils.testing import BotorchTestCase
  from gpytorch.kernels.matern_kernel import MaternKernel
  from gpytorch.kernels.rbf_kernel import RBFKernel
  from gpytorch.priors.torch_priors import GammaPrior, NormalPrior
  from gpytorch.test.base_kernel_test_case import BaseKernelTestCase
label_desc: Use image node_id 7 for calling the TestLinearTruncatedFidelityKernel obj's underlying member method code with example usage: obj.test_initialize_lengthscale_prior() without return types