code: def validate(self, form_cls, obj=None):
          '''Validate a form from the request and handle errors'''
          if 'application/json' not in request.headers.get('Content-Type'):
              errors = {'Content-Type': 'expecting application/json'}
              self.abort(400, errors=errors)
          form = form_cls.from_json(request.json, obj=obj, instance=obj,
                                    csrf_enabled=False)
          if not form.validate():
              self.abort(400, errors=form.errors)
          return forf validate(self, form_cls, obj=None):
          '''Validate a form from the request and handle errors'''
          if 'application/json' not in request.headers.get('Content-Type'):
              errors = {'Content-Type': 'expecting application/json'}
              self.abort(400, errors=errors)
          form = form_cls.from_json(request.json, obj=obj, instance=obj,
                                    csrf_enabled=False)
          if not form.validate():
              self.abort(400, errors=form.errors)
          return form
docs: Validate a form from the request and handle errors