    # File lib/gettext.rb, line 128
      def textdomain(domainname)
        domain = TextDomainManager.textdomain(domainname)
        raise NoboundTextDomainError, "#{domainname} is not bound." unless domain
        target_key = bound_target
        manager = @@__textdomainmanagers[target_key]
        unless manager
          manager = TextDomainManager.new(target_key, Locale.get)
          @@__textdomainmanagers[target_key] = manager
        end
        manager.set_locale(Locale.get)
        manager.add_textdomain(domainname)
        manager
      end