\makeatletter

\@ifclasslater{oblivoir}{2021/05/20}{}%
{%
	\def\obparttitlealignment{}
    \long\def\@part[#1]#2{%
      \M@gettitle{#1}%
      \def\f@rtoc{#1}%
      \@nameuse{part@f@rtoc@before@write@hook}%
      \phantomsection
      \mempreaddparttotochook
      \ifnum \c@secnumdepth >-2\relax
        \refstepcounter{part}%
        \addcontentsline{toc}{part}%
          {\protect\partnumberline{\hparttitlehead}\f@rtoc}%
        \mempartinfo{\thepart}{\f@rtoc}{#2}%
      \else
        \addcontentsline{toc}{part}{\f@rtoc}%
        \mempartinfo{}{\f@rtoc}{#2}%
      \fi
      \mempostaddparttotochook
      \partmark{#1}%
      {%
       \obparttitlealignment
       \interlinepenalty \@M
       \parskip\z@
       \normalfont
       \ifnum \c@secnumdepth >-2\relax
         \prepartnum \partnamenum \printpartnum \partnamenum \postpartnum
         \midpartskip
       \fi
       \printparttitle{#2}\par}%
      \@endpart}
}



\makeatother