docs: public void addLevel(int len, LevelStatus status) {
          if(lvl_idx + 1 > lvl_capa) {
              lvl_capa += YAML.ALLOC_CT;
              levels = YAML.realloc(levels, lvl_capa);
          }
          levels[lvl_idx] = new Level();
          levels[lvl_idx].spaces = len;
          levels[lvl_idx].ncount = 0;
          levels[lvl_idx].domain = levels[lvl_idx-1].domain;
          levels[lvl_idx].status = status;
          lvl_idx++;
      }