docs: function addToRegistry(rule) {
  		let name = rule.name;
  
  		if (registry.hasOwnProperty(name)) {
  			// `each` allows for safe looping while modifying the
  			// array being looped over. `append` is removing the rule
  			// from the array being looped over, so it is necessary
  			// to use this method instead of forEach 
  			rule.each(r => registry[name].append(r));
  		} else {
  			registry[name] = rule.clone();
  		}
  	}