tyle = new ol.style.Style({
            image: new ol.style.Circle({
              radius: 8,
              fill: new ol.style.Fill({color: 'rgba(255, 0, 0, 0.2)'}),
              stroke: new ol.style.Stroke({color: 'red', width: 1})
            }),
            text: new ol.style.Text({
              text: f.get('node').id.toString(),
              fill: new ol.style.Fill({color: 'red'}),
              stroke: new ol.style.Stroke({
                color: 'white',
                width: 3
              })
  