code: @Override
      public Promise<Void> writeFile(String path, Buffer data) {
          return adapter.toPromise(handler -> vertx.fileSystem().writeFile(path, data, handler));
      }
docs: Creates the file, and writes the specified {@code Buffer data} to the file represented by the path {@code path},
  asynchronously.
  
  @param path path to the file
  @param data
  @return a promise for completion