code: def upload_folder(self, bucket, folder, key=None, skip=None,
                        content_types=None):
          
          uploader = FolderUploader(self, bucket, folder, key, skip,
                                    content_types)
          return uploader.start()
docs: Recursively upload a ``folder`` into a backet.
  
          :param bucket: bucket where to upload the folder to
          :param folder: the folder location in the local file system
          :param key: Optional key where the folder is uploaded
          :param skip: Optional list of files to skip
          :param content_types: Optional dictionary mapping suffixes to
              content types
          :return: a coroutine