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._superApply(arguments);
  			// 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...