docs: def get_registered_instances(self, include_removed=False):
          """ Return the persisted names of all instances across all registered configs.
          """
          rval = []
          configs = self.state.get('config_files', {}).values()
          if include_removed:
              configs.extend(self.state.get('remove_configs', {}).values())
          for config in configs:
              if config['instance_name'] not in rval:
                  rval.append(config['instance_name'])
          return rval