interface StringIO {
  replace SomethingHead with StringHead.
  
  void readWrite(SomethingHead head);

  default S saveToString(SomethingHead head default new) {
    var writer = stringWriter();
    head.writer(writer);
    readWrite(head);
    head.finish();
    ret str(writer);
  }

  default File saveToTextFile(File file) {
    temp Writer out = bufferedFileWriter(file);
    var head = new SomethingHead(out);
    readWrite(head);
    head.finish();
    ret file;
  }
  
  default selfType load aka fromString(S data) {
    readWrite(new SomethingHead(stringReader(data)));
    this;
  }
  
  default selfType loadTextFile(File file) {
    temp var in = bufferedReader(file);
    readWrite(new SomethingHead(in));
    this;
  }
}

Began life as a copy of #1035635