code: def do_get_session(self, session_key):
          
          session_id = session_key.session_id
          msg = ("do_get_session: Attempting to retrieve session with key " +
                 str(session_id))
          logger.debug(msg)
  
          session = self._retrieve_session(session_key)
  
          if (session is not None):
              self.validate(session, session_key)
  
          return session
docs: :type session_key: SessionKey
          :returns: SimpleSession