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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def pages_dynamic_tree_menu(context, page, url='/'):
 """ Render a "dynamic" tree menu, with all nodes expanded which are either ancestors or the current page itself. Override ``pages/dynamic_tree_menu.html`` if you want to change the design. :param page: the current page :param url: not used anymore """

    lang = context.get('lang', pages_settings.PAGE_DEFAULT_LANGUAGE)
    page = get_page_from_string_or_id(page, lang)
    children = None
    if page and 'current_page' in context:
        current_page = context['current_page']
        # if this node is expanded, we also have to render its children
        # a node is expanded if it is the current node or one of its ancestors
        if(
            page.tree_id == current_page.tree_id and
            page.lft <= current_page.lft and
            page.rght >= current_page.rght
        ):
            children = page.get_children_for_frontend()
    context.update({'children': children, 'page': page})
    return context