code: async def post(self, request):
          
          form = await self.get_form(request)
          if not form.validate():
              raise muffin.HTTPBadRequest(
                  text=json.dumps(form.errors), content_type='application/json')
          await self.save_form(form, request)
          raise muffin.HTTPFound(self.url)
docs: Create/Edit items.