title: QuerySet has no field_names?
body: <p>So I'm currently upgrading a Django app from 1.8 to 3.1 and came upon the following error:</p>
  <p><code>AttributeError: 'QuerySet' object has no attribute 'field_names'</code></p>
  <p>I have tried to find deprecation information on this attribute and checked the QuerySet API for information but couldn't find anything relevant.</p>
  <p>Has anybody gone through the same?</p>