class_docstr: Router provides mapping from external address to internal address.
code: def get_internal_address(self, external_address: str) -> str:
      if external_address in self._curr_external_addresses:
          # local address, use dummy address
          return self._local_mapping.get(external_address)
      # try to lookup inner address from address mapping
      return self._mapping.get(external_address)
  
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 10 for calling the Router obj's underlying member method code with example usage: obj.get_internal_address(external_address) and returns: self, self