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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 xlsx_blob(self):
 """ Return the byte stream of an Excel file formatted as chart data for the category chart specified in the chart data object. """

        xlsx_file = BytesIO()
        with self._open_worksheet(xlsx_file) as (workbook, worksheet):
            self._populate_worksheet(workbook, worksheet)
        return xlsx_file.getvalue()