docs: def authenticateRequest(self, service_request, username, password, **kwargs):
          """
          Processes an authentication request. If no authenticator is supplied,
          then authentication succeeds.
  
          @return: C{Deferred}.
          @rtype: C{twisted.internet.defer.Deferred}
          """
          authenticator = self.getAuthenticator(service_request)
  
          if self.logger:
              self.logger.debug('Authenticator expands to: %r' % authenticator)
  
          if authenticator is None:
              return defer.succeed(True)
  
          args = (username, password)
  
          if hasattr(authenticator, '_pyamf_expose_request'):
              http_request = kwargs.get('http_request', None)
              args = (http_request,) + args
  
          return defer.maybeDeferred(authenticator, *args)