docs: public final <E> void register(final Class clazz, final String field, final SimpledCoder<R, W, E> coder) {
          if (field == null || clazz == null) return;
          try {
              clazz.getDeclaredField(field);
          } catch (Exception e) {
              throw new RuntimeException(clazz + " not found field(" + field + ")");
          }
          if (coder == null) {
              Map map = this.fieldCoders.get(clazz);
              if (map != null) map.remove(field);
          } else {
              this.fieldCoders.computeIfAbsent(clazz, c -> new ConcurrentHashMap<>()).put(field, coder);
          }
      }