Model for OSF APIv2 preprints. This model may be used with one of several API endpoints. It may be queried directly, or accessed via relationship fields. For field and usage information, see: https://api.osf.io/v2/docs/#!/v2/Preprint_List_GET https://api.osf.io/v2/docs/#!/v2/Preprint_Detail_GET https://api.osf.io/v2/docs/#!/v2/User_Preprints_GET