code: func newACLFilter(authorizer acl.Authorizer, logger *log.Logger, enforceVersion8 bool) *aclFilter {
  	if logger == nil {
  		logger = log.New(os.Stderr, "", log.LstdFlags)
  	}
  	return &aclFilter{
  		authorizer:      authorizer,
  		logger:          logger,
  		enforceVersion8: enforceVersion8,
  	}
  }
docs: // newACLFilter constructs a new aclFilter.