code: def test_lanczos_fantasy_model(self):
      lanczos_thresh = 10
      n = lanczos_thresh + 1
      n_dims = 2
      with settings.max_cholesky_size(lanczos_thresh):
          x = torch.ones((n, n_dims))
          y = torch.randn(n)
          likelihood = GaussianLikelihood()
          model = ExactGPModel(x, y, likelihood=likelihood)
          mll = ExactMarginalLogLikelihood(likelihood, model)
          mll.train()
          mll.eval()
  
          # get a posterior to fill in caches
          model(torch.randn((1, n_dims)))
  
          new_n = 2
          new_x = torch.randn((new_n, n_dims))
          new_y = torch.randn(new_n)
          # just check that this can run without error
          model.get_fantasy_model(new_x, new_y)
  
imports: import unittest
  import torch
  import gpytorch
  from gpytorch import settings
  from gpytorch.kernels import GridInterpolationKernel
  from gpytorch.likelihoods import GaussianLikelihood
  from gpytorch.mlls import ExactMarginalLogLikelihood
  from gpytorch.models import ExactGP
  from gpytorch.models.exact_prediction_strategies import InterpolatedPredictionStrategy
  from gpytorch.test.model_test_case import BaseModelTestCase
label_desc: Use image node_id 12 for calling the TestExactGP obj's underlying member method code with example usage: obj.test_lanczos_fantasy_model() without return types