docs: def authenticate_credentials(self, request, access_token):
          """
          Authenticate the request, given the access token.
          """
  
          try:
              token = oauth2_provider.oauth2.models.AccessToken.objects.select_related('user')
              # provider_now switches to timezone aware datetime when
              # the oauth2_provider version supports to it.
              token = token.get(token=access_token, expires__gt=provider_now())
          except oauth2_provider.oauth2.models.AccessToken.DoesNotExist:
              raise exceptions.AuthenticationFailed('Invalid token')
  
          user = token.user
  
          if not user.is_active:
              msg = 'User inactive or deleted: %s' % user.username
              raise exceptions.AuthenticationFailed(msg)
  
          return (user, token)