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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 _make_sections(self, **section_hdr_params):
 """Flatten the sections into a single story list."""

        sect_story = []
        if not self.section_headings and len(self.sections):
            self.section_headings = self.sections.keys()

        for section_name in self.section_headings:
            section_story = self.sections[section_name]
            line = '-'*20
            section_head_text = '%s %s %s' % (line, section_name, line)
            title, title_sp = self._preformat_text(section_head_text,
                                                   **section_hdr_params)
            sect_story += [title, title_sp] + section_story
        return sect_story