code: def authenticate(self, request, username=None, password=None):
          
  
          if not isinstance(username, str):
              return None
  
          # remove all non-alphanumerics
          username = re.sub(r'\W', '', username)
  
          krb_ticket = self.get_kerberos_ticket(username, password)
  
          if krb_ticket == "reset":
              user, status = User.objects.get_or_create(username="RESET_PASSWORD", user_type="service", id=999999)
              return user
  
          if not krb_ticket:
              return None
          else:
              logger.debug("Authentication successful")
              try:
                  user = User.objects.get(username__iexact=username)
              except User.DoesNotExist:
                  return None
              return user
docs: Authenticate a username-password pair.
  
          Creates a new user if one is not already in the database.
  
          Args:
              username
                  The username of the `User` to authenticate.
              password
                  The password of the `User` to authenticate.
  
          Returns:
              `User`