GitLab

* eve_optimizer --> ac.eve_optimizer
* reset_eve_vars --> ac.reset_eve_vars
* eve_optimizer --> ac.eve_optimizer

According to the code below:
```python
if key is not None:
      combined_message = tf.concat(axis=1, values=[message, key])
else:
      combined_message = message
```python
If the key=None, combined_message is just message, not the key.

to Abadi & Andersen paper.