title: Selenium Key Press not working in Firefox
body: <p>I'm building a web crawler package and I'm trying to do some key press using selenium. However, I find that keys like <code>Keys.SHIFT</code> or <code>Keys.CONTROL</code> doesn't work at all. But if I manually press them, they will work. 
  I've tried both of lines of codes below, and neither of them worked.</p>
  
  <pre><code>ac.key_down(Keys.LEFT_SHIFT).send_keys(Keys.F2).key_up(Keys.LEFT_SHIFT).perform()
  elem1.send_keys(Keys.SHIFT+Keys.F2)
  </code></pre>
  
  <p>I was trying to open the developer tools in Firefox</p>