docs: public long markNode(Object n) {
          long oid = 0;
          if(this.markers == null) {
              this.markers = new IdentityHashMap<Object, Long>();
          }
  
          if(!this.markers.containsKey(n)) {
              oid = this.markers.size() + 1;
              markers.put(n, oid);
          } else {
              oid = this.markers.get(n);
              if(this.anchors == null) {
                  this.anchors = new HashMap<Long, String>();
              }
              if(!anchors.containsKey(oid)) {
                  int idx = 0;
                  String anc = this.anchor_format == null ? YAML.DEFAULT_ANCHOR_FORMAT : this.anchor_format;
                  idx = anchors.size() + 1;
                  String anchor_name = String.format(anc, idx);
                  anchors.put(oid, anchor_name);
              }
          }
  
          return oid;
      }