code: private void write(LineString geom, JsonGenerator gen) throws IOException {
          gen.writeStringField("type", "LineString");
          gen.writeFieldName("coordinates");
          writeCoordinates(geom.getCoordinates(), gen);
      }
docs: Coordinates of LineString are an array of positions :
  
  { "type": "LineString", "coordinates": [ [100.0, 0.0], [101.0, 1.0] ] }
  
  @param geom
  @param gen
  @throws IOException