code: public static List<ExternalGraphic> externalGraphicsFromGraphic( Graphic graphic ) {
          List<ExternalGraphic> gList = new ArrayList<ExternalGraphic>();
          for( GraphicalSymbol gs : graphic.graphicalSymbols() ) {
              if ((gs != null) && (gs instanceof ExternalGraphic)) {
                  ExternalGraphic externalGraphic = (ExternalGraphic) gs;
                  gList.add(externalGraphic);
              }
          }
          return gList;
      }
docs: Collect all {@link ExternalGraphic}s from the given {@link Graphic}.
  
  @param graphic the graphic to check.
  @return the extracted {@link ExternalGraphic}s.