title: How to conditionally show fields in django admin if there is a value?
body: <p>in admin.py file I have a</p>
  
  <pre><code> fields = ('name', 'description', ('created_by','created', ),('updated_by', 'updated'))
  </code></pre>
  
  <p>How can I only show created, created_by if is NON blank. 
  When I about to create a new records, created_by, created, updated_by and updated is blank and I don't need to show them.</p>
  
  <p>Only when I save the records, I like to show these fields in django admin.</p>