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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 set_section_order(self, section_name_list):
 """Set the order of the sections, which are by default unorderd. Any unlisted sections that exist will be placed at the end of the document in no particular order. """

        self.section_headings = section_name_list[:]
        for section_name in self.sections.keys():
            if section_name not in section_name_list:
                self.section_headings.append(section_name)
        return