docs: def save_as(self, filename):
          """Download the attachment to a file.
  
          :param filename: File path
          :type filename: basestring
          :raises APIError: When unable to download the data
          :raises OSError: When unable to save the data to disk
          """
          with open(filename, 'w+b') as f:
              for chunk in self._download():
                  f.write(chunk)