docs: def _read_configuration_file(self, config_filename):
          """
          Reads parameters from the configuration file.
  
          :param str config_filename: The name of the configuration file.
          """
          config = configparser.ConfigParser()
          config.read(config_filename)
  
          self._source_directory = config.get('loader', 'source_directory')
          self._source_file_extension = config.get('loader', 'extension')
          self._source_file_encoding = config.get('loader', 'encoding')
          self.__shadow_directory = config.get('loader', 'shadow_directory', fallback=None)
  
          self._pystratum_metadata_filename = config.get('wrapper', 'metadata')
  
          self._constants_class_name = config.get('constants', 'class')