code: def determine_version(self, request, *args, **kwargs):
          
          if self.versioning_class is None:
              return (None, None)
          scheme = self.versioning_class()
          return (scheme.determine_version(request, *args, **kwargs), scheme)
docs: If versioning is being used, then determine any API version for the
          incoming request. Returns a two-tuple of (version, versioning_scheme)