code: func NewBackend(delegateBackend audit.Backend, config Config, groupVersion schema.GroupVersion) audit.Backend {
  	return &backend{
  		delegateBackend: delegateBackend,
  		c:               config,
  		e:               audit.Codecs.LegacyCodec(groupVersion),
  	}
  }
docs: // NewBackend returns a new truncating backend, using configuration passed in the parameters.
  // Truncate backend automatically runs and shut downs the delegate backend.