docs: public final void seek(String key) {
          if (key == null || key.length() < 1) return;
          final String[] keys = key.split("\\.");
          nextGoodChar(); //读掉 { [
          for (String key1 : keys) {
              while (this.hasNext()) {
                  String field = this.readSmallString();
                  readBlank();
                  if (key1.equals(field)) break;
                  skipValue();
              }
          }
  
      }