code: def download_file(self, file_id, dest):
          
          f = self.getFile(file_id)
          try:
              d = dest if _isfile(dest) else open(dest, 'wb')
  
              r = api.download((self._token, f['file_path']), preload_content=False)
  
              while 1:
                  data = r.read(self._file_chunk_size)
                  if not data:
                      break
                  d.write(data)
          finally:
              if not _isfile(dest) and 'd' in locals():
                  d.close()
  
              if 'r' in locals():
                  r.release_conn()
docs: Download a file to local disk.
  
          :param dest: a path or a ``file`` object