It doesnt appear to be a regular log norm pdf as seen in <https://en.wikipedia.org/wiki/Log-normal_distribution> 

<https://www.tensorflow.org/tutorials/generative/cvae>

```
def log_normal_pdf(sample, mean, logvar, raxis=1):
  log2pi = tf.math.log(2. * np.pi)
  return tf.reduce_sum(
      -.5 * ((sample - mean) ** 2. * tf.exp(-logvar) + logvar + log2pi),
      axis=raxis)

```