def _get_expand_head_file_path(config):
 return os.path.join(_get_root_versions_dir(config), EXPAND_HEAD_FILENAME)

def _get_expand_head_file_path ( config ) : return os . path . join ( _get_root_versions_dir ( config ) , EXPAND_HEAD_FILENAME )
return the path of the file that is used to maintain expand head .