docs: function(open, close) {
      this.fieldOpen = (typeof open === 'string' && open.length) ? open : '____';
      this.fieldClose = (typeof close === 'string' && close.length) ? close : this.fieldOpen;
      
      var fieldPattern = this.fieldOpen +'(.+?)'+ this.fieldClose;
      this.fieldRegex = new RegExp(fieldPattern);
      this.fieldRegexAll = new RegExp(fieldPattern, 'g');
    }