https://github.com/pfnet/sold/pull/15/files#diff-85551712891dd189f0d52838cfecfaae71363ed28ab58ab38ceaf990aaf1585bR28-R31
https://github.com/pfnet/sold/pull/15/files#diff-85551712891dd189f0d52838cfecfaae71363ed28ab58ab38ceaf990aaf1585bR28-R31