code: def load_replace_candidate(self, filename=None, config=None):
          
          self.config_replace = True
          return_status, msg = self._load_candidate_wrapper(source_file=filename,
                                                            source_config=config,
                                                            dest_file=self.candidate_cfg,
                                                            file_system=self.dest_file_system)
          if not return_status:
              raise ReplaceConfigException(msg)
docs: SCP file to device filesystem, defaults to candidate_config.
  
          Return None or raise exception