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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 json_formatter(subtitles):
 """ Serialize a list of subtitles as a JSON blob. """

    subtitle_dicts = [
        {
            'start': start,
            'end': end,
            'content': text,
        }
        for ((start, end), text)
        in subtitles
    ]
    return json.dumps(subtitle_dicts)