Why not re-use session for various inputs?

[trollyxia]

In generate.py, it seems that for every input, the generate() function will create a new session and do session.run():

parallel-wavenet-vocoder/generate.py

Line 50 in 6c2fa06

with tf.Session(config=session_config) as sess:

I'm just wondering, will this approach incur session creation overhead every time? Why not create a session once and re-use the session as most of the other models do?