code: def get_element_by_id(self, ident):
          
          for group in list(self.toc.keys()):
              for name in list(self.toc[group].keys()):
                  if self.toc[group][name].ident == ident:
                      return self.toc[group][name]
          return None
docs: Get a TocElement element identified by index number from the
          container.