title: How to call `getEventListeners` in GreaseMonkey
body: <p>I'm try to write a user script in GreaseMonkey/TamperMonkey. I want to delete all <code>copy</code> listeners. But it seems that <code>getEventListeners</code> is undefined in the sandbox.</p>
  
  <p>I've tried <code>unsafeWindow</code>, but the <code>getEventListeners</code> is still missing.</p>
  
  <p>Is there a way to call it in the GreaseMonkey environment?</p>
  
  <p>Or are there any methods can I remove all <code>copy</code> listeners?</p>