code: public void addMarker(T marker) {
  
          final MarkerOptions markerOptions = new MarkerOptions();
          marker.setMarkerManager(this);
          marker.prepareMarker(markerOptions);
  
          markerCache.put(marker, googleMap.addMarker(markerOptions));
  
          marker.onAdd();
      }
docs: Add a marker to the map.
  
  @param marker marker to add