code: def test_constant_offset(self, is_scalar=True):
      offset_ = (
          np.array(3.1415)
          if is_scalar
          else np.array([3.0, 1.0, 4.0, 1.0, 5.0])
      )
      offset = self._build_placeholder(offset_)
      ssm = self._dummy_model()
  
      additive_ssm = AdditiveStateSpaceModel([ssm])
      additive_ssm_with_offset = AdditiveStateSpaceModel(
          [ssm], constant_offset=offset
      )
      additive_ssm_with_offset_and_explicit_scale = (
          AdditiveStateSpaceModel(
              [ssm],
              constant_offset=offset,
              observation_noise_scale=(
                  ssm.get_observation_noise_for_timestep(0).stddev()[
                      ..., 0
                  ]
              ),
          )
      )
  
      mean_, offset_mean_, offset_with_scale_mean_ = self.evaluate(
          (
              additive_ssm.mean(),
              additive_ssm_with_offset.mean(),
              additive_ssm_with_offset_and_explicit_scale.mean(),
          )
      )
      self.assertAllClose(
          mean_, offset_mean_ - offset_[..., tf.newaxis]
      )
      self.assertAllClose(
          mean_, offset_with_scale_mean_ - offset_[..., tf.newaxis]
      )
  
      # Offset should not affect the stddev.
      (
          stddev_,
          offset_stddev_,
          offset_with_scale_stddev_,
      ) = self.evaluate(
          (
              additive_ssm.stddev(),
              additive_ssm_with_offset.stddev(),
              additive_ssm_with_offset_and_explicit_scale.stddev(),
          )
      )
      self.assertAllClose(stddev_, offset_stddev_)
      self.assertAllClose(stddev_, offset_with_scale_stddev_)
  
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 11 for calling the _AdditiveStateSpaceModelTest obj's underlying member method code with example usage: obj.test_constant_offset(is_scalar) without return types