public function revokeRank($rank)
 {
     if (is_array($rank)) {
         $revokeReason = $rank['reason'];
         $rank = Rank::findOrFail($rank['model']->id);
     }
     if ($rank->count() && empty($rank->revoked_at)) {
         $this->getRankPivotBuilder($rank->id)->update(['revoke_reason' => $revokeReason, 'revoked_at' => Carbon::now()]);
     }
 }