code: async def parse_json(self, req: Request, name: str, field: Field) -> typing.Any:
          
          json_data = self._cache.get("json")
          if json_data is None:
              if not (req.body_exists and is_json_request(req)):
                  return core.missing
              try:
                  json_data = await req.json(loads=json.loads)
              except json.JSONDecodeError as e:
                  if e.doc == "":
                      return core.missing
                  else:
                      return self.handle_invalid_json_error(e, req)
              self._cache["json"] = json_data
          return core.get_value(json_data, name, field, allow_many_nested=True)
docs: Pull a json value from the request.