title: Dynamically filter pk in queryset
body: <p>My generic DetailView:</p>
  
  <pre><code>class CircularDetail(DeleteView):
      model = Circular
      template_name = 'genre/circular_detail.html'
  
      def get_context_data(self, **kwargs):
          ctx = super(CircularDetail, self).get_context_data(**kwargs)
          ctx['c'] = Circular.objects.get(pk=1)
          ctx['sittings'] = Sitting.objects.all()
  
          return ctx
  </code></pre>
  
  <p>My circular model:</p>
  
  <pre><code>class Circular(models.Model):
      cir_no = models.IntegerField(blank=False)
      sit_start_date = models.DateField(blank=False)
      sit_end_date = models.DateField(blank=False)
      sess_no = models.ForeignKey(Session,
                                   on_delete=models.CASCADE)
      parl_no = models.ForeignKey(Parliament,
                                  on_delete=models.CASCADE)
      class Meta:
          unique_together = ('cir_no', 'sess_no',)
  </code></pre>
  
  <p>This only shows when pk=1 but I want to assign pk values dynamically so that when I chose different pk it gives corresponding data in view.</p>
  
  <p>How can I assign pk values dynamically?</p>