/** @param container must not be null. */
 public static IonWriter makeSystemWriter(IonContainer container) {
   IonSystem sys = container.getSystem();
   IonCatalog cat = sys.getCatalog();
   SymbolTable defaultSystemSymtab = sys.getSystemSymbolTable();
   IonWriter writer =
       new IonWriterSystemTree(defaultSystemSymtab, cat, container, null /* initialIvmHandling */);
   return writer;
 }
 /** @param container must not be null. */
 public static IonWriter makeWriter(IonContainer container) {
   IonSystem sys = container.getSystem();
   IonCatalog cat = sys.getCatalog();
   IonWriter writer = makeWriter(cat, container);
   return writer;
 }