docs: def select_site_view(self, request, form_url=''):
          """
          Display a choice form to select which site to add settings.
          """
          if not self.has_add_permission(request):
              raise PermissionDenied
  
          extra_qs = ''
          if request.META['QUERY_STRING']:
              extra_qs = '&' + request.META['QUERY_STRING']
  
          site_choices = self.get_site_choices()
  
          if len(site_choices) == 1:
              return HttpResponseRedirect('?site_id={0}{1}'.format(site_choices[0][0], extra_qs))
  
          # Create form
          form = self.select_site_form(
              data=request.POST if request.method == 'POST' else None,
              initial={'site': site_choices[0][0]}
          )
  
          form.fields['site'].choices = site_choices
  
          if form.is_valid():
              return HttpResponseRedirect(
                  '?site_id={0}{1}'.format(form.cleaned_data['site'], extra_qs))
  
          # Wrap in all admin layout
          fieldsets = ((None, {'fields': ('site',)}),)
          adminForm = AdminForm(form, fieldsets, {}, model_admin=self)
          media = self.media + adminForm.media
  
          context = {
              'title': _('Add %s') % force_text(self.opts.verbose_name),
              'adminform': adminForm,
              'is_popup': '_popup' in request.GET,
              'media': mark_safe(media),
              'errors': AdminErrorList(form, ()),
              'app_label': self.opts.app_label,
          }
  
          return self.render_select_site_form(request, context, form_url)