title: How to set dictionary values to null
body: <p>I'm wondering if there is a way to put all dictionary values to null (or each elements) ? Because we can't iterate on it if the values has been changed to null.</p>
  
  <p>(I've searched on Stackoverflow before asking this simple question but I didn't find a clear response on this issue). </p>
  
  <p>Regards</p>