docs: function(doctype){
      var ast = [];
      if (doctype && (doctype.val || !this.doctype)) {
        this.setDoctype(doctype.val || 'html');
      }
  
      if (this.doctype) push.apply(ast, this.buffer(this.doctype));
      this.hasCompiledDoctype = true;
      return ast;
    }