code: def test_multivariate_observations(self):
      seed = test_util.test_seed(sampler_type="stateless")
  
      # since STS components are scalar by design, we manually construct
      # a multivariate-output model to verify that the additive SSM handles
      # this case.
      num_timesteps = 5
      observation_size = 2
      multivariate_ssm = self._dummy_model(
          num_timesteps=num_timesteps, observation_size=observation_size
      )
  
      # Note it would not work to specify observation_noise_scale here;
      # multivariate observations need to derive the (multivariate)
      # observation noise distribution from their components.
      combined_ssm = AdditiveStateSpaceModel(
          [multivariate_ssm, multivariate_ssm]
      )
  
      y = combined_ssm.sample(seed=seed)
      expected_event_shape = [num_timesteps, observation_size]
      if self.use_static_shape:
          self.assertAllEqual(
              tensorshape_util.as_list(combined_ssm.event_shape),
              expected_event_shape,
          )
          self.assertAllEqual(
              tensorshape_util.as_list(y.shape)[-2:],
              expected_event_shape,
          )
      else:
          self.assertAllEqual(
              self.evaluate(combined_ssm.event_shape_tensor()),
              expected_event_shape,
          )
          self.assertAllEqual(
              self.evaluate(tf.shape(y))[-2:], expected_event_shape
          )
  
imports: from absl.testing import parameterized
  import numpy
  import tensorflow.compat.v1
  import tensorflow.compat.v2
  from tensorflow_probability.python.distributions import linear_gaussian_ssm
  from tensorflow_probability.python.distributions import mvn_diag
  from tensorflow_probability.python.internal import tensorshape_util
  from tensorflow_probability.python.internal import test_util
  from tensorflow_probability.python.sts.components.local_linear_trend import LocalLinearTrendStateSpaceModel
  from tensorflow_probability.python.sts.components.sum import AdditiveStateSpaceModel
label_desc: Use image node_id 5 for calling the _AdditiveStateSpaceModelTest obj's underlying member method code with example usage: obj.test_multivariate_observations() without return types