What is BOOST_FILESYSTEM_VERSION 3 analog for BOOST_FILESYSTEM_VERSION 2 path.native_file_string()?

Question

So I try to port my old project (from boost 1.44 to 1.61) I found out that there is no path.native_file_string() in boost::filesystem v3...

So what is analog for path.native_file_string() in boost::filesystem v3? (I do not want to use v2 any more but I need such functionality as native_file_string)