<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def set_default_locale(code: str) -> None: """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. """

    global _default_locale
    global _supported_locales
    _default_locale = code
    _supported_locales = frozenset(list(_translations.keys()) + [_default_locale])