code: function() {
      var str
        , prefix;
      this.expect('namespace');
  
      this.skipSpacesAndComments();
      if (prefix = this.accept('ident')) {
        prefix = prefix.val;
      }
      this.skipSpacesAndComments();
  
      str = this.accept('string') || this.url();
      this.allowPostfix = true;
      return new nodes.Namespace(str, prefix);
    }
docs: namespace ident? (string | url)