private function flushBuffer(): void
    {
        if (null !== $this->passthruLevel) {
            $level = $this->passthruLevel;
            $this->buffer = array_filter($this->buffer, function ($record) use ($level) {
                return $record['level'] >= $level;
            });
            if (count($this->buffer) > 0) {
                $this->handler->handleBatch($this->buffer);
            }
        }

        $this->buffer = [];
        $this->buffering = true;
    }