> For the complete documentation index, see [llms.txt](https://docs.abbey.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.abbey.io/reference/access-policies/helper-functions.md).

# Helper Functions

Abbey has created a number of helper functions to help write policies. First you need to write `import data.abbey.functions` to import the helper functions and then you can start using any helper function you'd like.

## in\_group(group\_name)

The `in_group` function tests whether an Abbey user belongs to a certain group. To check whether a user is in a group named `Engineering`, you can write `in_group("Engineering")`.

Look [here](https://github.com/abbeylabs/policy-library/blob/main/src/abbey/functions/in_group.rego) for the source.

## has\_attribute(attribute\_name, attribute\_value)

The `has_attribute` function tests whether an Abbey user has a certain attribute. For example, to check if a user has an Employee Type of `IC`, you can write `has_attribute("employee_type", "IC")`. `attribute_name` can be the name of any attribute on a user from your IDP and `attribute_value` can be any string.

Look [here](https://github.com/abbeylabs/policy-library/blob/main/src/abbey/functions/has_attribute.rego) for the source.

## expire\_at(ts)

The `expire_at` function denies a policy at a certain timestamp `ts`. For example, if you write `expire_at("2023-01-01T02:00:00Z")`, then this will deny the policy at any time after `2023-01-01T02:00:00Z`. Abbey continues to check for whether a policy will be expiring at a later date, allowing you to write time-based expiry policies.

Look [here](https://github.com/abbeylabs/policy-library/blob/main/src/abbey/functions/expire_at.rego) for the source.

## expire\_after(duration)

The `expire_after` function denies a policy after a certain amount of time has passed. For example, to deny a policy after 30 minutes, you can write `expire_after("30m")`. Like `expire_at,` Abbey continues to check whether an `expire_after` policy has expired so that policies will actually deny after their  given time.

The `duration` argument needs an integer concatenated with a unit, so something like `30s`, `60m`, `3h`, or `1d`. The exact `duration` syntax is documented [here](https://pkg.go.dev/time#ParseDuration).

Look [here](https://github.com/abbeylabs/policy-library/blob/main/src/abbey/functions/expire_after.rego) for the source.