midPointPlacemarkOnlyTag method
Property that defines the tour midPointPlacemarkOnlyTag according to its current properties.
Implementation
String midPointPlacemarkOnlyTag(double lat, double long, String styleID) {
  String content = '';
  //  <styleUrl>#placemark-$placemarkIndex-style</styleUrl>
  content += '''
<Placemark>
    <styleUrl>#$styleID</styleUrl>
    <Point>
      <coordinates>$long,$lat,0</coordinates>
    </Point>
  </Placemark>
''';
  return content;
}