class_docstr: Router provides mapping from external address to internal address.
code: def set_mapping(self, mapping: Dict[str, str]):
      self._mapping = mapping
      self._cache_local = threading.local()
  
file_path: mars/mars/oscar/backends/router.py
imports: import threading
  from typing import Dict, List, Tuple, Type, Any, Optional
  from .communication import get_client_type, Client
label_desc: Use image node_id 6 for calling the Router obj's underlying member method code with example usage: obj.set_mapping(mapping) without return types