def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def reset_should_print_backtrace_to_terminal(cls, should_print_backtrace):
        """Set whether a backtrace gets printed to the terminal error stream on a fatal error.

        Class state:
        - Overwrites `cls._should_print_backtrace_to_terminal`.
        """
        cls._should_print_backtrace_to_terminal = should_print_backtrace