code: def parse_config_files(self, filenames=None, ignore_option_errors=False):
          
          self._parse_config_files(filenames=filenames)
  
          parse_configuration(self, self.command_options,
                              ignore_option_errors=ignore_option_errors)
          self._finalize_requires()
docs: Parses configuration files from various levels
          and loads configuration.