code: function(ctx){
  		var tree = this, // same as ctx.tree,
  			opts = ctx.options,
  			extOpts = ctx.options.childcounter;
  // Optionally check for dependencies with other extensions
  		/* this._requireExtension("glyph", false, false); */
  // Call the base implementation
  		this._super(ctx);
  // Add a class to the tree container
  		this.$container.addClass("fancytree-ext-childcounter");
  	}
docs: /* Init `treeInit` is triggered when a tree is initalized. We can set up classes or bind event handlers here...