title: Django - filter model
body: <p>I have a model with a field that is a list.
  For example:</p>
  
  <pre><code>mymodel.sessions = [session1, session2]
  </code></pre>
  
  <p>I need a query to get all <code>mymodels</code> that <code>session1</code> is exist their sessions.</p>
  
  <p>The model`s field looks like that</p>
  
  <pre><code>sessions = models.ForeignKey("Session", related_name="abstracts",
                                  null=True, blank=True)
  </code></pre>
  
  <p>Thank you !</p>