Downloads the data associated with this instance
        Return:
          mp3_directory (os.path): The directory into which the associated mp3's were downloaded

def download(self):
        """Downloads the data associated with this instance
        Return:
          mp3_directory (os.path): The directory into which the associated mp3's were downloaded
        """
        mp3_directory = self._pre_download()
        self.data.swifter.apply(func=lambda arg: self._download(*arg, mp3_directory), axis=1, raw=True)
        return mp3_directory