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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 sheets_service(self):
 """ A SpreadsheetsService singleton, used to perform operations on the actual spreadsheet. """

        if not hasattr(self, '_sheets_service'):
            service = SpreadsheetsService()
            service.email = self.google_user
            service.password = self.google_password
            service.source = SOURCE_NAME
            service.ProgrammaticLogin()
            self._sheets_service = service
        return self._sheets_service