code: @Override
      public Promise<AsyncFile> open(String path, OpenOptions options) {
          return adapter.toPromise(handler -> vertx.fileSystem().open(path, options, handler));
      }
docs: Open the file represented by {@code path}, asynchronously.
  <p>
  The file is opened for both reading and writing. If the file does not already exist it will be created.
  
  @param path    path to the file
  @param options options describing how the file should be opened
  @return a promise for the async file