[Question] `positional` argument with at least one value mandatory

Is there a way to specify that a positional arg need at least one value?

```rust
#[derive(FromArgs)]
/// MyCMD
struct Opt {
#[argh(positional)]
/// script files to run
test_file: Vec,
}
```
gives me:
```
Usage: mycmd.exe []
```
Which suggests the tool can work without any input when it needs at least one.