Callback method for rule tree traversing. Will be called at proper time
        from :py:class:`pynspect.rules.ListRule.traverse` method.

        :param pynspect.rules.Rule rule: Reference to rule.
        :param dict kwargs: Optional callback arguments.

def list(self, rule, **kwargs):
        """
        Callback method for rule tree traversing. Will be called at proper time
        from :py:class:`pynspect.rules.ListRule.traverse` method.

        :param pynspect.rules.Rule rule: Reference to rule.
        :param dict kwargs: Optional callback arguments.
        """
        return '<ul class="pynspect-rule-list">{}</ul>'.format(''.join(['<li class="pynspect-rule-list-item">{}</li>'.format(v.traverse(self, **kwargs)) for v in rule.value]))