docs: def guess_filename(self, basedir, kind=None):
          """
          Try to find existing settings filename from base directory using
          default filename from available engines.
  
          First finded filename from available engines win. So registred engines
          order matter.
  
          Arguments:
              basedir (string): Directory path where to search for.
  
          Keyword Arguments:
              kind (string): Backend engine kind name to search for default
                  settings filename. If not given, search will be made for
                  default settings filename from all available backend engines.
  
          Returns:
              tuple: Absolute filepath and backend engine class.
          """
          if kind:
              filepath = os.path.join(basedir,
                                      self.engines[kind]._default_filename)
              if os.path.exists(filepath):
                  return filepath, self.engines[kind]
  
          for filename, kind in self.filenames.items():
              filepath = os.path.join(basedir, filename)
              if os.path.exists(filepath):
                  return filepath, self.engines[kind]
  
          msg = "Unable to find any settings in directory: {}"
          raise SettingsDiscoveryError(msg.format(basedir))