*
   * {@snippet :
   * static final ImmutableClassToInstanceMap<Handler> HANDLERS =
   *     new ImmutableClassToInstanceMap.Builder<Handler>()
   *         .put(FooHandler.class, new FooHandler())
   *         .put(BarHandler.class, new SubBarHandler())
   *         .put(Handler.class, new QuuxHandler())
   *         .build();
   * }
   *

   *
   * {@snippet :
   * static final ImmutableClassToInstanceMap<Handler> HANDLERS =
   *     new ImmutableClassToInstanceMap.Builder<Handler>()
   *         .put(FooHandler.class, new FooHandler())
   *         .put(BarHandler.class, new SubBarHandler())
   *         .put(Handler.class, new QuuxHandler())
   *         .build();
   * }
   *

   *
   * {@snippet :
   * static final ImmutableTypeToInstanceMap<Handler<?>> HANDLERS =
   *     ImmutableTypeToInstanceMap.<Handler<?>>builder()
   *         .put(new TypeToken<Handler<Foo>>() {}, new FooHandler())
   *         .put(new TypeToken<Handler<Bar>>() {}, new SubBarHandler())
   *         .build();
   * }
   *
   * <p>After invoking {@link #build()} it is still possible to add more entries and build again.