title: mocking session in requests library
body: <p>In my python code I have global <code>requests.session</code> instance:</p>
  
  <pre><code>import requests
  session = requests.session()
  </code></pre>
  
  <p>How can I mock it with <code>Mock</code>? Is there any decorator for this kind of operations? I tried following:</p>
  
  <pre><code>session.get = mock.Mock(side_effect=self.side_effects)
  </code></pre>
  
  <p>but (as expected) this code doesn't return <code>session.get</code> to original state after each test, like <code>@mock.patch</code> decorator do.</p>