title: ImportError: cannot import name 'SkipWrapper' from 'gym.wrappers'
body: <p>When I want to import SkipWrapper It occurs an error</p>
  <pre><code>from gym.wrappers import SkipWrapper  
  ImportError: cannot import name 'SkipWrapper' from 'gym.wrappers'
  </code></pre>
  <p>I can't find any solution on the internet. I tried to downgrade gym to 0.9.5 but It also doesn't work.</p>