code: def test_structure_8(backend):
      def model():
          i_plate = pyro.plate("i", 2, dim=-1)
          with i_plate:
              a = pyro.sample("a", dist.Normal(0, 1))
          b = pyro.sample("b", dist.Normal(a.mean(-1), 1))
          with i_plate:
              pyro.sample("c", dist.Normal(b, 1), obs=torch.ones(2))
  
      # size = 2 + 1 = 3
      structure = [
          "? ? ?",
          "? ? ?",
          "? ? ?",
      ]
      if backend == "funsor":
          check_backends_agree(model)
      else:
          check_structure(model, structure)
  
imports: from collections import OrderedDict, namedtuple
  import pytest
  import torch
  import pyro
  import pyro.distributions
  import pyro.poutine
  from pyro.infer import SVI, JitTrace_ELBO, Predictive, Trace_ELBO
  from pyro.infer.autoguide import AutoGaussian, AutoGuideList
  from pyro.infer.autoguide.gaussian import AutoGaussianDense, AutoGaussianFunsor, _break_plates
  from pyro.infer.reparam import LocScaleReparam
  from pyro.optim import ClippedAdam
  from tests.common import assert_close, assert_equal, xfail_if_not_implemented
label_desc: Use image node_id 13 for calling a global function with example usage: test_structure_8(backend) without return types