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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 get_download_url(self, file):
 """ Creates a url to download the file. Note: Contains the secret API key, so you should not share this url! :param file: The File you want to get the url to download. :type file: pytgbot.api_types.receivable.media.File :return: url :rtype: str """

        from .api_types.receivable.media import File
        assert isinstance(file, File)
        return file.get_download_url(self.api_key)