code: function ($edge) {
        var $chart = this.$chart;
        if (typeof $chart.data('inAjax') !== 'undefined' && $chart.data('inAjax') === true) {
          return false;
        }
  
        $edge.addClass('hidden');
        $edge.parent().append('<i class="fa fa-circle-o-notch fa-spin spinner"></i>')
          .children().not('.spinner').css('opacity', 0.2);
        $chart.data('inAjax', true);
        $('.oc-export-btn' + (this.options.chartClass !== '' ? '.' + this.options.chartClass : '')).prop('disabled', true);
        return true;
      }
docs: start up loading status for requesting new nodes