How do I employ cache busting in a template?

^{Originally posted by **ugyballoons** July 22, 2022}
Hi,
I'm enjoying working with aiohttp and jinja2.
It's not clear to me how to employ cache busting. Please could someone help?
In the setup I have:
```
sub_app.add_routes(
[
web.static(
"/static",
Path(__file__).parent / "static",
name="static",
append_version=True,
),
]
)
sub_app["static_root_url"] = "/path-to/static"
env = aiohttp_jinja2.get_env(sub_app)
env.globals.update(
zip=zip,
url_for=web.Resource.url_for
)
```
and in the template I have:
``

I feel that I shouldn't be passing `url_for` in the globals but if I don't, then jinja complains that there's no such function. Where am I going wrong?