core-bundle/src/Resources/contao/classes/Versions.php
protected function getUserId()
	{
		if ($this->intUserId !== null)
		{
			return $this->intUserId;
		}

		$this->import(BackendUser::class, 'User');

		return $this->User->id;
	}
protected function getUserId()
	{
		if ($this->intUserId !== null)
		{
			return $this->intUserId;
		}

		$this->import(BackendUser::class, 'User');

		return $this->User->id;
	}
Return the user ID

@return string