code: def authenticate_credentials(self, userargs, password, request=None):
          
  
          credentials = {
              'password': password
          }
  
          if "=" not in userargs:
              # if it doesn't seem to be in querystring format, just use it as the username
              credentials[get_user_model().USERNAME_FIELD] = userargs
          else:
              # parse out the user args from querystring format into the credentials dict
              for arg in userargs.split("&"):
                  key, val = arg.split("=")
                  credentials[key] = val
  
          # authenticate the user via Django's auth backends
          user = authenticate(**credentials)
  
          if user is None:
              raise exceptions.AuthenticationFailed('Invalid credentials.')
  
          if not user.is_active:
              raise exceptions.AuthenticationFailed('User inactive or deleted.')
  
          return (user, None)
docs: Authenticate the userargs and password against Django auth backends.
          The "userargs" string may be just the username, or a querystring-encoded set of params.