code: @Deprecated
      public int numThreadLocalCaches() {
          PoolArena<?>[] arenas = heapArenas != null ? heapArenas : directArenas;
          if (arenas == null) {
              return 0;
          }
  
          int total = 0;
          for (PoolArena<?> arena : arenas) {
              total += arena.numThreadCaches.get();
          }
  
          return total;
      }
docs: Return the number of thread local caches used by this {@link PooledByteBufAllocator}.
  
  @deprecated use {@link PooledByteBufAllocatorMetric#numThreadLocalCaches()}.