So if you want to write a Queryset in Django like this:

  models.MyModel.objects.filter( Q(a=1) | Q(b=2).extra(where=[""]) )

It desn't work, because extra() can not be used on a django.db.models.Q object

Instead, you can write like this:

  qs = models.MyModel.objects.filter(a=1)
  qs |= models.MyModel.objects.filte(b=2).extra(where=[""])

I guess it's cool.