code: def set_config_file(self, path):
          
          log = self._params.get('log', self._discard)
          if path != self._config_file:
              if self._config_file:
                  log.info("Config file changed from '%s' to '%s'", self._config_file, path)
                  self.file_del(self, paths=[self._config_file])
              else:
                  log.info("Config file set to '%s'", path)
              self._config_file = path
              self.file_add(event_target(self, 'legion_config', log=log), path)
          return self._load_config()
docs: Set the config file.  The contents must be valid YAML and there
          must be a top-level element 'tasks'.  The listed tasks will be
          started according to their configuration, and the file will
          be watched for future changes.  The changes will be activated
          by appropriate changes to the running tasks.