code: def get_configuration_file():
      
      path = os.path.abspath(os.curdir)
      while path != os.sep:
          config_path = os.path.join(path, CONFIG_FILE_NAME)
          if os.path.exists(config_path):
              return config_path
          path = os.path.dirname(path)
      return None
docs: return jenks configuration file