lookup error at router

[shubham joshi]

I my users api  - > https://github.com/shubham1507/school/blob/trial/users/urls.py

HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

{
    "teacher": "http://127.0.0.1:8000/users/teacher/",
    "student": "http://127.0.0.1:8000/users/student/"
}



whenever I hit to either of the link 
"http://127.0.0.1:8000/users/teacher/",or 
 "http://127.0.0.1:8000/users/student/" then 


Could not resolve URL for hyperlinked relationship using view name "user-detail". You may have failed to include the related model in your API, or incorrectly configured the `lookup_field` attribute on this field.