# File lib/googleauth/user_authorizer.rb, line 126
      def get_credentials user_id, scope = nil
        saved_token = stored_token user_id
        return nil if saved_token.nil?
        data = MultiJson.load saved_token

        if data.fetch("client_id", @client_id.id) != @client_id.id
          raise format(MISMATCHED_CLIENT_ID_ERROR,
                       data["client_id"], @client_id.id)
        end

        credentials = UserRefreshCredentials.new(
          client_id:     @client_id.id,
          client_secret: @client_id.secret,
          scope:         data["scope"] || @scope,
          access_token:  data["access_token"],
          refresh_token: data["refresh_token"],
          expires_at:    data.fetch("expiration_time_millis", 0) / 1000
        )
        scope ||= @scope
        return monitor_credentials user_id, credentials if credentials.includes_scope? scope
        nil
      end