docstr: Test that when a PosteriorList has one posterior, result of
  `scalarize_posterior` matches result of calling `scalarize_posterior`
  on that posterior.
code: def test_scalarize_posterior_one_posterior(self) -> None:
      """
      Test that when a PosteriorList has one posterior, result of
      `scalarize_posterior` matches result of calling `scalarize_posterior`
      on that posterior.
      """
      m = 1
      for batch_shape, lazy, dtype in itertools.product(
          ([], [3]), (False, True), (torch.float, torch.double)
      ):
          tkwargs = {"device": self.device, "dtype": dtype}
          offset = torch.rand(1).item()
          weights = torch.randn(m, **tkwargs)
          # Make sure the weights are not too small.
          while torch.any(weights.abs() < 0.1):
              weights = torch.randn(m, **tkwargs)
          # test q=1
          posterior = _get_test_posterior(
              batch_shape, m=m, lazy=lazy, **tkwargs
          )
          posterior_list = PosteriorList(posterior)
          new_posterior = scalarize_posterior(
              posterior, weights, offset
          )
          new_post_from_list = scalarize_posterior(
              posterior_list, weights, offset
          )
          self.assertEqual(
              new_posterior.mean.shape, new_post_from_list.mean.shape
          )
          self.assertAllClose(
              new_posterior.mean, new_post_from_list.mean
          )
          self.assertTrue(
              torch.allclose(
                  new_posterior.variance, new_post_from_list.variance
              )
          )
  
file_path: botorch/test/posteriors/test_posteriorlist.py
imports: import itertools
  import torch
  from botorch.posteriors.gpytorch import scalarize_posterior
  from botorch.posteriors.posterior_list import PosteriorList
  from botorch.utils.testing import _get_test_posterior, BotorchTestCase
label_desc: Use image node_id 2 for calling the TestPosteriorList obj's underlying member method code with example usage: obj.test_scalarize_posterior_one_posterior() without return types