def METHOD_NAME(
    cls: t.Type[CredentialSelf], new_default: t.Optional[CredentialSelf], src: str
) -> t.ContextManager[None]:
    """
    Set the default (highest preferred) credentials manually.
    They won't be checked for validity until a future get()
    This call can be used as contextmanager to unset within a `with` statement
    """
    cls._DEFAULT = new_default
    cls._DEFAULT_SRC = src
    return cls._unset_default_context()