docs: public void _serializeStruct(Struct struct, StringBuilder sb, Set<Object> done) throws ConverterException {
  	sb.append(goIn());
  	sb.append('{');
  	Iterator it = struct.keyIterator();
  	boolean doIt = false;
  	deep++;
  	while (it.hasNext()) {
  	    String key = Caster.toString(it.next(), "");
  	    if (doIt) sb.append(',');
  	    doIt = true;
  	    sb.append(QUOTE_CHR);
  	    sb.append(escape(key));
  	    sb.append(QUOTE_CHR);
  	    sb.append(':');
  	    _serialize(struct.get(key, null), sb, done);
  	}
  	deep--;
  
  	sb.append('}');
      }