writeString method
override
    Writes a string to the file using the given Encoding.
Returns a Future<RandomAccessFile> that completes with this
random access file when the write completes.
Implementation
@override
Future<io.RandomAccessFile> writeString(
  String string, {
  Encoding encoding = utf8,
}) async {
  await delegate.writeString(string, encoding: encoding);
  return this;
}