core/src/com/google/inject/multibindings/Multibinder.java
public static <T> Multibinder<T> newSetBinder(Binder binder, Key<T> key) {
    return new Multibinder<T>(newRealSetBinder(binder.skipSources(Multibinder.class), key));
  }
public static <T> Multibinder<T> newSetBinder(Binder binder, Key<T> key) {
    return new Multibinder<T>(newRealSetBinder(binder.skipSources(Multibinder.class), key));
  }
Returns a new multibinder that collects instances of the key's type in a {@link Set} that is
itself bound with the annotation (if any) of the key.

@since 4.0