def arrange_serializable options={}, nodes=nil, &block
      nodes = arrange(options) if nodes.nil?
      nodes.map do |parent, children|
        if block_given?
          yield parent, arrange_serializable(options, children, &block)
        else
          parent.serializable_hash.merge 'children' => arrange_serializable(options, children)
        end
      end
    end
def arrange_serializable options={}, nodes=nil, &block
      nodes = arrange(options) if nodes.nil?
      nodes.map do |parent, children|
        if block_given?
          yield parent, arrange_serializable(options, children, &block)
        else
          parent.serializable_hash.merge 'children' => arrange_serializable(options, children)
        end
      end
    end
Arrangement to nested array