func (set *PackageReferenceSet) Remove(ref PackageReference) {
	delete(set.references, ref)
}
Remove ensures the specified item is not present
Removing an item not in the set is not an error.
package astmodel
import "sort"
type PackageReferenceSet struct {
	references map[PackageReference]struct{}
}
func NewPackageReferenceSet(refs ...PackageReference) *PackageReferenceSet {
	result := &PackageReferenceSet{
		references: make(map[PackageReference]struct{}),
	}
	for _, ref := range refs {
		result.AddReference(ref)
	}
	return result
}
func (set *PackageReferenceSet) AddReference(ref PackageReference) {
	set.references[ref] = struct{}{}
}
func (set *PackageReferenceSet) Merge(other *PackageReferenceSet) {
	for ref := range other.references {
		set.AddReference(ref)
	}
}