code: def mid_elements_masked(
      transition_matrix, transition_cov, transition_mean
  ):
      """Represents messages from masked values at non-initial timesteps."""
      with tf.name_scope("mid_elements_masked"):
          return FilterElements(
              posterior_link_matrix=transition_matrix,
              posterior_mean=transition_mean,
              posterior_cov=transition_cov,
              marginal_likelihood_meanprec=tf.zeros_like(
                  transition_mean
              ),
              marginal_likelihood_prec=tf.zeros_like(transition_cov),
          )
  
imports: import collections
  import functools
  import numpy
  import tensorflow.compat.v2
  from tensorflow_probability.python.distributions import mvn_tril
  from tensorflow_probability.python.internal import dtype_util
  from tensorflow_probability.python.internal import prefer_static
  from tensorflow_probability.python.internal import samplers
  from tensorflow_probability.python.math import linalg
  from tensorflow_probability.python.math.scan_associative import scan_associative
label_desc: Use image node_id 8 for calling a global function with example usage: mid_elements_masked(transition_matrix, transition_cov, transition_mean) and returns: FilterElements