code: def _check_section_option(self, section, option):
          
          if section is None:
              section = self.DEFAULT_SECTION_NAME
          elif not is_text_string(section):
              raise RuntimeError("Argument 'section' must be a string")
          if not is_text_string(option):
              raise RuntimeError("Argument 'option' must be a string")
          return section
docs: Private method to check section and option types