Iteratively analyze function features until a fixed point is reached.

        :return: the "changes" dict
        :rtype:  dict

def _iteratively_analyze_function_features(self, all_funcs_completed=False):
        """
        Iteratively analyze function features until a fixed point is reached.

        :return: the "changes" dict
        :rtype:  dict
        """

        changes = {
            'functions_do_not_return': set(),
            'functions_return': set()
        }

        while True:
            new_changes = self._analyze_function_features(all_funcs_completed=all_funcs_completed)

            changes['functions_do_not_return'] |= set(new_changes['functions_do_not_return'])
            changes['functions_return'] |= set(new_changes['functions_return'])

            if not new_changes['functions_do_not_return'] and not new_changes['functions_return']:
                # a fixed point is reached
                break

        return changes