core/src/com/google/inject/multibindings/MapBinder.java
public static <K, V> MapBinder<K, V> newMapBinder(
      Binder binder, TypeLiteral<K> keyType, TypeLiteral<V> valueType) {
    return new MapBinder<K, V>(
        newMapRealBinder(binder.skipSources(MapBinder.class), keyType, valueType));
  }
public static <K, V> MapBinder<K, V> newMapBinder(
      Binder binder, TypeLiteral<K> keyType, TypeLiteral<V> valueType) {
    return new MapBinder<K, V>(
        newMapRealBinder(binder.skipSources(MapBinder.class), keyType, valueType));
  }
Returns a new mapbinder that collects entries of {@code keyType}/{@code valueType} in a {@link
Map} that is itself bound with no binding annotation.