You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: mbox.rb
    path of file: ./repos/imap-backup/lib/imap/backup/serializer
    
    the code of the file until where you have to start completion: require "imap/backup/serializer/transaction"

module Imap; end

module Imap::Backup
  class Serializer; end

  # Stores messages
  class Serializer::Mbox
    # @return [String] The path of the mailbox file, without the '.mbox' extension
    attr_reader :folder_path

    # @param folder_path [String] The path of the mailbox file, without the '.mbox' exten
    
    def transaction(&block)
      tsx.fail_in_transaction!(:transaction, message: "nested transactions are not supported")

      tsx.begin({savepoint: {length: length}}) do
        block.call
      rescue StandardError => e
        rollback
        raise e
      rescue SignalException => e
        Logger.logger.error "#{self.class} handling #{e.class}"
        rollback
        raise e
      end
    end