code: def set_default_locale(code: str) -> None:
      
      global _default_locale
      global _supported_locales
      _default_locale = code
      _supported_locales = frozenset(list(_translations.keys()) + [_default_locale])
docs: Sets the default locale.
  
      The default locale is assumed to be the language used for all strings
      in the system. The translations loaded from disk are mappings from
      the default locale to the destination locale. Consequently, you don't
      need to create a translation file for the default locale.