question: how to validate `array.length`?

I am using nestjs+gql it's the code

```ts
@InputType()
export class InsertSessionsInput {
  @Max(1000, { message: 'limit 1000 items' })
  @Field(() => [InMemoSession])
  sessions: InMemoSession[];
}
```
**The problem:**

it check the length of `object.toString()` not the length of array,