pub fn is_unrestricted(&self) -> bool {
        matches!(self, PackagePublish::Unrestricted)
    }
Returns true if this package can be published to any package registry.

# Examples

```
use guppy::graph::PackagePublish;

assert!(PackagePublish::Unrestricted.is_unrestricted());
assert!(!PackagePublish::Registries(&[PackagePublish::CRATES_IO.to_owned()]).is_unrestricted());
assert!(!PackagePublish::Registries(&[]).is_unrestricted());
```
guppy/src/graph/graph_impl.rs