docs: @Nullable
      private ThreadPoolExecutor unwrapThreadPoolExecutor(ExecutorService executor, Class<?> wrapper) {
          try {
              Field e = wrapper.getDeclaredField("e");
              e.setAccessible(true);
              return (ThreadPoolExecutor) e.get(executorService);
          } catch (NoSuchFieldException | IllegalAccessException e) {
              // Do nothing. We simply can't get to the underlying ThreadPoolExecutor.
          }
          return null;
      }