AssignableTo provides the ability to filter registered types to those types that are assignable to the provided type, which will typically be a marker interface type, although any interface type will do.

InPackage provides the ability to filter registered types to those that are in a particular package or set of packages.

ListTypes queries the global component registry.

RegisterType adds a type to the global component registry.

Registry is captured as a type here so that you can stub out implementations of it in your tests.

Option to the ListTypes function.