persistable sclass AbstractSSIList extends NotifyingList<AbstractSSI> {
  *() { init(); }
  *(Cl<? extends AbstractSSI> l) { initAndAddAll(importSSIs(l)); }
  
  L<AbstractSSI> importSSIs(Cl<? extends AbstractSSI> l) {
    ret map importSSI(l);
  }
  
  // overridable
  AbstractSSI importSSI(AbstractSSI ssi) {
    ret ssi;
  }
  
  BufferedImage render(WidthAndHeight size) {
    ret renderAll(this, size);
  }
  
  BufferedImage render(BufferedImage canvas) {
    ret renderAll(this, canvas);
  }
  
  BufferedImage renderOutlines(WidthAndHeight size) {
    ret toSSIList().renderOutlines(size);
  }
  
  SSIList toSSIList() {
    ret new SSIList(map(this, -> .toSSI()));
  }
}