code: public static void registerSerializers(final Kryo kryo) {
  
          // ImmutableMap is used by ImmutableMultimap. However,
          // we already have a separate serializer class for ImmutableMap,
          // ImmutableMapSerializer. If it is not already being used, register it.
          Serializer immutableMapSerializer = getSerializer(kryo, ImmutableMap.class);
          if (!(immutableMapSerializer instanceof ImmutableMapSerializer)) {
              ImmutableMapSerializer.registerSerializers(kryo);
          }
  
          // ImmutableList is used by ImmutableListMultimap. However,
          // we already have a separate serializer class for ImmutableList,
          // ImmutableListSerializer. If it is not already being used, register it.
          Serializer immutableListSerializer = getSerializer(kryo, ImmutableList.class);
          if (!(immutableListSerializer instanceof ImmutableListSerializer)) {
              ImmutableListSerializer.registerSerializers(kryo);
          }
  
          // ImmutableSet is used by ImmutableSetMultimap. However,
          // we already have a separate serializer class for ImmutableSet,
          // ImmutableSetSerializer. If it is not already being used, register it.
          Serializer immutableSetSerializer = getSerializer(kryo, ImmutableSet.class);
          if (!(immutableSetSerializer instanceof ImmutableSetSerializer)) {
              ImmutableSetSerializer.registerSerializers(kryo);
          }
  
          final ImmutableMultimapSerializer serializer = new ImmutableMultimapSerializer();
  
          // ImmutableMultimap (abstract class)
          //  +- EmptyImmutableListMultimap
          //  +- ImmutableListMultimap
          //  +- EmptyImmutableSetMultimap
          //  +- ImmutableSetMultimap
  
          kryo.register(ImmutableMultimap.class, serializer);
          kryo.register(ImmutableListMultimap.of().getClass(), serializer);
          kryo.register(ImmutableListMultimap.of("A", "B").getClass(), serializer);
          kryo.register(ImmutableSetMultimap.of().getClass(), serializer);
          kryo.register(ImmutableSetMultimap.of("A", "B").getClass(), serializer);
      }
docs: Creates a new {@link ImmutableMultimapSerializer} and registers its serializer
  for the several ImmutableMultimap related classes.
  
  @param kryo the {@link Kryo} instance to set the serializer on