code: public static function unregister(?array $signals = null): void
      {
          if (empty($signals)) {
              $signals = self::KNOWN_SIGNALS;
          }
  
          foreach ($signals as $signal) {
              if (is_string($signal)) {
                  // skip missing signals, for example OSX does not have all signals
                  if (!defined($signal)) {
                      continue;
                  }
  
                  $signal = constant($signal);
              }
  
              pcntl_signal($signal, SIG_DFL);
          }
      }
docs: Clear all previously registered signal handlers.
  
  @param  string[]|int[]|null $signals
  @return void