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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 export_xlsx(self, key):
 """ Download xlsx version of spreadsheet. """

        spreadsheet_file = self.client.files().get(fileId=key).execute()
        links = spreadsheet_file.get('exportLinks')
        downloadurl = links.get('application/vnd.openxmlformats-officedocument.spreadsheetml.sheet')
        resp, content = self.client._http.request(downloadurl)
        return content