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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _extract_id(self) -> str: """ Get video_id needed to obtain the real_url of the video. Raises: VideoIdNotMatchedError: If video_id is not matched with regular expression. """

        match = re.match(self._VALID_URL, self.url)

        if match:
            return match.group('video_id')
        else:
            raise VideoIdNotMatchedError