docs: function(){
      var tok = this.expect('extends');
      var path = this.expect('path');
      return {
        type: 'Extends',
        file: {
          type: 'FileReference',
          path: path.val.trim(),
          line: path.loc.start.line,
          column: path.loc.start.column,
          filename: this.filename
        },
        line: tok.loc.start.line,
        column: tok.loc.start.column,
        filename: this.filename
      };
    }