def each(&block)
      Enumerator.new do |y|
        @rules.each do |key, node|
          y << entry_to_rule(node, key)
        end
      end.each(&block)
    end
def each(&block)
      Enumerator.new do |y|
        @rules.each do |key, node|
          y << entry_to_rule(node, key)
        end
      end.each(&block)
    end
Iterates each rule in the list.