text: JSONEditor.defaults.iconlibs.materialicons = JSONEditor.AbstractIconLib.extend({
  
      mapping: {
          collapse: 'arrow_drop_up',
          expand: 'arrow_drop_down',
          "delete": 'delete',
          edit: 'edit',
          add: 'add',
          cancel: 'cancel',
          save: 'save',
          moveup: 'arrow_upward',
          movedown: 'arrow_downward',
          copy: 'content_copy'
      },
  
      icon_class: 'material-icons',
      icon_prefix: '',
  
      getIconClass: function(key) {
  
          // This method is unused.
  
          return this.icon_class;
      },
  
      getIcon: function(key) {
  
          // Get the mapping.
          var mapping = this.mapping[key];
          if (!mapping) return null;
  
          // @see http://materializecss.com/icons.html
          var i = document.createElement('i');
          i.className = this.icon_class;
          var t = document.createTextNode(mapping);
          i.appendChild(t);
          return i;
  
      }
  });
  