gistfile1.txt

    def page(self):
        modules = self.object.course_instance.published_modules
        for index, module in enumerate(modules):
            if module == self.object:
                prev_i = index - 1
                next_i = index + 1
                break

        previous_module = modules[prev_i] if prev_i >= 0 else None
        next_module = modules[next_i] if next_i < len(modules) else None

        return {
            "previous": previous_module,
            "next": next_module,
        }
        
  
  
  <section>
        {% if vew.page.previous %}
            <a href="{% url 'courseinstancemodule_detail' courseinstancemodule.course_instance.slug view.page.previous.id %}">Previous</a>
        {% else %}
            <a href="{% url 'course_instance_detail' courseinstancemodule.course_instance.slug %}">Previous</a>
        {% endif %}

        {% if vew.page.next %}
            <a href="{% url 'courseinstancemodule_detail' courseinstancemodule.course_instance.slug view.page.next.id %}">Next</a>
        {% endif %}
    </section>

    DEBUG:
    Previous: <History of the Symphony [initial version]: Lesson One for History of the Symphony>
    Next: <History of the Symphony [initial version]: Lesson Three for History of the Symphony>