title: Error importing keras backend - cannot import name has_arg
body: <p>i attempt to import keras backend to get_session as follows, but i encounter an error:
  <a href="https://i.stack.imgur.com/CQHYI.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/CQHYI.png" alt="enter image description here"></a></p>