title: Use prefetched data on django form to set field queryset
body: <p>I am not sure how to set form fields using prefetched data. I am fetching a questionnaire section and then pre fetching the questions in the section.</p>
  <p>The idea if that the questions for the section will be available in the section condition choices form.</p>
  <p>Query</p>
  <pre><code> questionnaire_sections = Section.objects.prefetch_related(
                  
                  Prefetch(
                      'question_set',
                      queryset=Question.objects.all(),
                      to_attr=&quot;questions&quot;
                  )
  
              ),
  
          )
  
  </code></pre>
  <p>This works:</p>
  <pre><code>for section in  questionnaire_sections
       questions = Question.objects.filter(section=section)
  
       condition_form = QuestionnaireConditionForm()
       condition_form.fields[&quot;item&quot;].queryset = questions
       section.condition_form = condition_form
  </code></pre>
  <p>But it i try to use prefetched data like below to save queries, I get error below.</p>
  <pre><code>for section in  questionnaire_sections
       questions = section.questions
  
       condition_form = QuestionnaireConditionForm()
       condition_form.fields[&quot;item&quot;].queryset = questions
       section.condition_form = condition_form
  </code></pre>
  <p>Error:</p>
  <pre><code>AttributeError: 'list' object has no attribute 'all'
  </code></pre>
  <p>The error is quite obvious, but I am wondering if I can actually populate form choices using prefetched data at all?</p>