title: Get QuerySet from ForeignKey in Django
body: <p>I have two models in Django:</p>
  <pre><code>class Category(models.Model)
     ....
  
  class Article(models.Model)
     category=models.ForeignKey(Category,on_delete=models.CASCADE,blank=True,null=True)
  </code></pre>
  <p>I would like to get some categories with some filter, and all the articles of this Category in the same Query.</p>
  <p>I try with annotate, but I do not know how is the correct syntax.</p>
  <pre><code>categories = Category.objets.filter(whatever='whatever').annotate('article')
  </code></pre>