code: def get_root_pattern(cls):
      return "/api/session(?:/(?P<sub_path>[^/]*)$|$)"
  
file_path: mars/mars/services/session/api/web.py
imports: import json
  from typing import Callable, Dict, List, Union
  from ....utils import parse_readable_size
  from ...web import web_api, MarsServiceWebAPIHandler, MarsWebAPIClientMixin
  from ..core import SessionInfo
  from .core import AbstractSessionAPI
label_desc: Use image node_id 1 for calling the SessionWebAPIHandler obj's underlying member method code with example usage: obj.get_root_pattern(cls) and returns: str