code: protected function parseRule(RuleCollection $collection, $name, array $config, $path)
      {
          $expression = isset($config['expression']) ? $config['expression'] : null;
          $tags = isset($config['tags']) ? $this->parseTags($config['tags']) : array();
  
          $rule = new Rule($expression);
  
          foreach ($tags as $tagName => $tagAttr) {
              $rule->addTag($tagName, $tagAttr);
          }
  
          $collection->add($name, $rule);
      }
docs: Parses a rule and adds it to the RuleCollection.
  
  @param RuleCollection $collection A RouteCollection instance
  @param string         $name       Rule name
  @param array          $config     Rule definition
  @param string         $path       Full path of the YAML file being processed