human
Complete the below
@register.tag
def ifinstalled(parser, token):

    ''''Old-style ``if`` tag that renders contents if the given app is
    installed. The main use case is:
    {% ifinstalled app_name %}
    {% include "app_name/template.html" %}
    {% endifinstalled %}
    so we need to manually pull out all tokens if the app isn\'t
    installed, since if we used a normal ``if`` tag with a False arg,
    the include tag will still try and find the template to include.'
    '''
assistant
#Here is Python program to find the template to include.
    try:
        (tag, app) = token.split_contents()
    except ValueError:
        raise TemplateSyntaxError(u'ifinstalled    should    be    in    the    form:    {%    ifinstalled    app_name    %}{%    endifinstalled    %}')
    end_tag = (u'end' + tag)
    unmatched_end_tag = 1
    if (app.strip(u'"\'') not in settings.INSTALLED_APPS):
        while unmatched_end_tag:
            token = parser.tokens.pop(0)
            if (token.token_type == TOKEN_BLOCK):
                block_name = token.contents.split()[0]
                if (block_name == tag):
                    unmatched_end_tag += 1
                if (block_name == end_tag):
                    unmatched_end_tag -= 1
        parser.tokens.insert(0, token)
    nodelist = parser.parse((end_tag,))
    parser.delete_first_token()
    class IfInstalledNode(Node, ):
        def render(self, context):
            return nodelist.render(context)
    return IfInstalledNode()