How to use the @igo2/geo.createOverlayMarkerStyle function in @igo2/geo

private getMarkerStyle(feature: Feature) {
    if (!feature.geometry || feature.geometry.type === 'Point') {
      return createOverlayMarkerStyle({text: feature.meta.mapTitle, opacity: 0.5});
    } else if (feature.geometry.type === 'LineString' || feature.geometry.type === 'MultiLineString') {
      return createOverlayDefaultStyle({text: feature.meta.mapTitle, strokeOpacity: 0.5});
    } else {
      return createOverlayDefaultStyle({text: feature.meta.mapTitle, fillOpacity: 0.15});
    }
  }

private getSelectedMarkerStyle(feature: Feature)  {
    if (!feature.geometry || feature.geometry.type === 'Point') {
      return createOverlayMarkerStyle({text: feature.meta.mapTitle});
    } else {
      return createOverlayDefaultStyle({text: feature.meta.mapTitle});
    }
  }