Can't render data from GAE datastore with Jinja2

I can't realize what I do wrong. I have some entries in GAE datastore. I have Jinja2 imported. I want to show datastore entries on the page using Jinja2. I have created a shortcut function to call Jinja2 render function. It looks like this:

def render_template(response, template_name, vars=dict()):
    template_dirs = [os.path.join(root(), globals['templates_root'])]
    env = Environment(loader=FileSystemLoader(template_dirs))
    try:
        template = env.get_template(template_name)
    except TemplateNotFound:
        raise TemplateNotFound(template_name)
    content = template.render(vars)
    response.response.out.write(content)

So, only thing I have to pass to this function is a template file name and a dictionary with variables if present. I call this function like this:

class MainHandler(webapp.RequestHandler):
    def get(self, *args, **kwargs):
        q = db.GqlQuery("SELECT * FROM Person")
        persons = q.fetch(20)
        utils.render_template(self, 'persons.html', persons)开发者_JS百科

The model Person looks like this, nothing fancy there:

class Person(db.Model):
    first_name = db.StringProperty()
    last_name = db.StringProperty()
    birth_date = db.DateProperty()

When I try to pass persons dictionary to render_template, it throws an error:

TypeError: cannot convert dictionary update sequence element #0 to a sequence

And it doesn't render. When I pass empty {} as persons argument, it renders, but obviously without my data. What do I do wrong? I am sure there is something small I missed but I have no idea what exactly. Thanks!

You're passing a list of entities to your render_template function instead of passing a dict. Try something like utils.render_template(self, 'persons.html', {'persons': persons})