Highlights: The new async/await keywords in Python 3.5 are supported.
In most cases, async def can be used in place of the @
gen.coroutine decorator. Inside a function defined with async def, use await instead of yield to wait on an asynchronous operation. Coroutines defined with async/await will be faster than those defined with @
gen.coroutine and yield.
But do not support some features including Callback/Wait or the ability to yield a Twisted Deferred. See the users ’ guide for more.
http://www.tornadoweb.org/en/stable/releases/v4.3.0.html