Checklist

• I have verified that that issue exists against the master branch of Django REST framework.
• I have searched for similar issues in both open and closed tickets and cannot find a duplicate.
• This is not a usage question. (Those should be directed to the discussion group instead.)
• This cannot be dealt with as a third party library. (We prefer new functionality to be in the form of third party libraries where possible.)
• I have reduced the issue to the simplest possible case.
• I have included a failing test as a pull request. (If you are unable to do so we can still accept the issue.)

Hello, thanks for this awesome piece of software!
The issue is the following:
When using detail_route in ModelViewSet and using "options" method , the documentation page fails with an exception.

Steps to reproduce

1. Create a project with ModelViewSet
2. Add this method in the class

@detail_route(methods=['options', 'get', 'put'])
def test(self, request, *args, **kwargs):
  pass

3. Check that the documentation is not working

Expected behavior

The documentation should work using the "options" method

Actual behavior

The documentation page is crashing with exception
KeyError: 'options'

Thanks for the help!
Amit.