How to get RESTful APIs documents(JSON file)

Currently, only the V3 version of the API specification document could be found.[https://api.apis.guru/v2/specs/gitlab.com/v3/swagger.json] The official website[API Docs | GitLab] only has the online description, and there is no specification file with all the APIs together. How could I get the entire API-v4 specification document, either in JSON or YAML format?