code: function($content){
        this.$instance.removeClass(this.namespace+'-loading');
  
        /* we need a special class for the iframe */
        this.$instance.toggleClass(this.namespace+'-iframe', $content.is('iframe'));
  
        /* replace content by appending to existing one before it is removed
           this insures that featherlight-inner remain at the same relative
           position to any other items added to featherlight-content */
        this.$instance.find('.'+this.namespace+'-inner')
          .not($content)                /* excluded new content, important if persisted */
          .slice(1).remove().end()      /* In the unexpected event where there are many inner elements, remove all but the first one */
          .replaceWith($.contains(this.$instance[0], $content[0]) ? '' : $content);
  
        this.$content = $content.addClass(this.namespace+'-inner');
  
        return this;
  		}
docs: /* sets the content of $instance to $content