docs: public static void shutdown() {
          if (MetricsManager.executorService != null) {
              MetricsManager.executorService.shutdown();
              MetricsManager.executorService = null;
          }
          if (MetricsManager.instance != null) {
              MetricsManager.instance = null;
              MetricsManager.poolManager.shutdown();
              MetricsManager.poolManager = null;
              MetricsManager.httpClient = null;
              MetricsManager.rootMetricsLogger = null;
          }
      }