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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 __update_filter(self):
 """ Create a combined filter. Set the resulting filter into the document controller. """

        filters = list()
        if self.__date_filter:
            filters.append(self.__date_filter)
        if self.__text_filter:
            filters.append(self.__text_filter)
        self.document_controller.display_filter = ListModel.AndFilter(filters)