docs: def render_pictures(context, selection='recent', amount=3):
      """Template tag to render a list of pictures."""
      pictures = Image.objects.filter(
          folder__id__in=Gallery.objects.filter(is_published=True).values_list(
              'folder__pk', flat=True))
      if selection == 'recent':
          context.update({
              'pictures': pictures.order_by('-uploaded_at')[:amount]
          })
      elif selection == 'random':
          context.update({
              'pictures': pictures.order_by('?')[:amount]
          })
      else:
          return None
      return context