@Test
 public void serializedForm() {
   Verify.assertSerializedForm(
       1L,
       "rO0ABXNyAHdjb20uZ3MuY29sbGVjdGlvbnMuaW1wbC5tYXAuaW1tdXRhYmxlLnByaW1pdGl2ZS5B\n"
           + "YnN0cmFjdEltbXV0YWJsZU9iamVjdExvbmdNYXAkSW1tdXRhYmxlT2JqZWN0TG9uZ01hcFNlcmlh\n"
           + "bGl6YXRpb25Qcm94eQAAAAAAAAABDAAAeHB3BAAAAAJ0AAEydwgAAAAAAAAAAnQAATF3CAAAAAAA\n"
           + "AAABeA==",
       new ImmutableObjectLongHashMap<String>(
           ObjectLongHashMap.newWithKeysValues("1", 1L, "2", 2L)));
 }
 public <V1> ObjectLongMap<V1> sumByLong(
     Function<V, V1> groupBy, LongFunction<? super V> function) {
   ObjectLongHashMap<V1> result = ObjectLongHashMap.newMap();
   return this.injectInto(result, PrimitiveFunctions.sumByLongFunction(groupBy, function));
 }