> For the complete documentation index, see [llms.txt](https://error.angular-package.dev/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://error.angular-package.dev/commonerrors/properties/id.md).

# #id?

## `#id?`

An optional collection of unique allowed [identification](/getting-started/basic-concepts.md#unique-identification) numbers of generic type variable [`Id`](/commonerrors/generic-type-variables.md#commonerrors-less-than-id-greater-than) under which errors are stored.

{% code title="common-errors.class.ts" %}

```typescript
#id?: Set<Id>;
```

{% endcode %}

### Type

#### `Set<`[<mark style="color:green;">`Id`</mark>](/commonerrors/generic-type-variables.md#commonerrors-less-than-id-greater-than)`>`