title: What is the g object in this Flask code?
body: <p>I found this code that times each response, but I'm not sure where <code>g</code> is supposed to come from.  What is <code>g</code>?</p>
  
  <pre><code>@app.before_request
  def before_request():
    g.start = time.time()
  
  @app.teardown_request
  def teardown_request(exception=None):
      diff = time.time() - g.start
      print diff
  </code></pre>