docs: def tokml(self):
          """Generate a KML Placemark element subtree.
  
          Returns:
              etree.Element: KML Placemark element
          """
          placemark = create_elem('Placemark')
          if self.name:
              placemark.set('id', self.name)
              placemark.name = create_elem('name', text=self.name)
          if self.description:
              placemark.description = create_elem('description',
                                                  text=self.description)
          placemark.Point = create_elem('Point')
  
          data = [str(self.longitude), str(self.latitude)]
          if self.altitude:
              if int(self.altitude) == self.altitude:
                  data.append('%i' % self.altitude)
              else:
                  data.append(str(self.altitude))
          placemark.Point.coordinates = create_elem('coordinates',
                                                    text=','.join(data))
  
          return placemark