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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_to_csv(self, infile, worksheet=0, delimiter=","):
 """ Convert xlsx to easier format first, since we want to use the convenience of the CSV library """

        wb = load_workbook(self.getInputFile())
        sheet = wb.worksheets[worksheet]
        buffer = StringIO()

        # extract all rows
        for n, row in enumerate(sheet.rows):
            line = []
            for cell in row:
                value = cell.value
                if type(value) in types.StringTypes:
                    value = value.encode("utf8")
                if value is None:
                    value = ""
                line.append(str(value))
            print >>buffer, delimiter.join(line)
        buffer.seek(0)
        return buffer