code: def download_all(self, dst_dir=None):
          
          saved = {}
          save_as = None
          for f in self.files():
              if dst_dir:
                  save_as = os.path.join(dst_dir, f.split('/')[-1])
              name, bytes = self.download(f, save_as)
              saved[name] = bytes
          return saved
docs: Download all available files.
  
          Arguments:
          dst_dir   -- Optional destination directory to write files to.  If not
                       specified, then files are downloaded current directory.
  
          Return:
          Dictionary of {file_name: file_size, ..}