docs: public Marker getMarker(String name) {
          if (name == null) {
              throw new IllegalArgumentException("Marker name cannot be null");
          }
  
          Marker marker = markerMap.get(name);
          if (marker == null) {
              marker = new BasicMarker(name);
              Marker oldMarker = markerMap.putIfAbsent(name, marker);
              if (oldMarker != null) {
                  marker = oldMarker;
              }
          }
          return marker;
      }