code: def _expand_str(path_cfg, alias_dict, overriding_kargs):
      
  
      if path_cfg in alias_dict:
          # e.g., path_cfg = 'var_cut'
          return _expand_str_alias(path_cfg, alias_dict, overriding_kargs)
  
      # e.g., path_cfg = 'ev : {low} <= ev.var[0] < {high}'
      return _expand_for_lambda_str(path_cfg, alias_dict, overriding_kargs)
docs: expand a path config given as a string