code: def __create_lists_for_nav_bar(self):
          
          
          nav_bar_section = []
          nav_bar_section_page = []
          for key in self.sections:
              nav_bar_section.append(key)
              nav_bar_page = []
              for page in self.sections[key].pages:
                  nav_bar_page.append(page)
              nav_bar_section_page.append(nav_bar_page)
          
          nav_bar_section_page_len = [len(x) for x in nav_bar_section_page]
          
          self.nav_bar_section_page = nav_bar_section_page # create a variable for later
          
          # nav_bar_page is a list of lists
          return nav_bar_section, nav_bar_section_page, nav_bar_section_page_len
docs: This method is called by __create_template_vars_index.
          Once the index is created, self.nav_bar_section_page is available for each page.