def get_child_story(self):
        logger.debug('# get_child_story')
        """
        try child story that match message and get scope of it
        :return:
        """
        story_loop = self.compiled_story()
        if hasattr(story_loop, 'children_matcher') and not self.matched:
            return self.get_story_scope_child(story_loop)

        story_part = self.get_current_story_part()

        if not hasattr(story_part, 'get_child_by_validation_result'):
            logger.debug('# does not have get_child_by_validation_result')
            return None

        if isinstance(self.waiting_for, forking.SwitchOnValue):
            logger.debug('# switch on value')
            return story_part.get_child_by_validation_result(self.waiting_for.value)

        # for some base classes we could try validate result direct
        child_story = story_part.get_child_by_validation_result(self.waiting_for)
        if child_story:
            logger.debug('# child_story')
            logger.debug(child_story)
            return child_story

        stack_tail = self.stack_tail()
        if stack_tail['data'] is not None and not self.matched:
            validator = matchers.deserialize(stack_tail['data'])
            logger.debug('# validator')
            logger.debug(validator)
            logger.debug('# self.message')
            logger.debug(self.message)
            validation_result = validator.validate(self.message)
            logger.debug('# validation_result')
            logger.debug(validation_result)
            res = story_part.get_child_by_validation_result(validation_result)
            logger.debug('# res')
            logger.debug(res)
            # or we validate message
            # but can't find right child story
            # maybe we should use independent validators for each story here
            if res is None:
                return self.get_story_scope_child(story_part)
            else:
                return res

        return None
try child story that match message and get scope of it
        :return: