### Question:
MetadataUpdateParams { public static Builder builder() { return builder(null); } MetadataUpdateParams(
            @JsonProperty("key") MetadataKey key,
            @JsonProperty("doc") String doc,
            @JsonProperty("attributes") Map<String, ?> attributes); MetadataKey getKey(); String getDoc(); Map<String, Object> getAttributes(); @Override int hashCode(); @Override boolean equals(Object obj); @Override String toString(); Builder toBuilder(); static Builder builder(); static Builder builder(MetadataUpdateParams origin);  }### Answer:
@Test public void testSerializedToJsonAndBack() throws Exception { MetadataUpdateParams origin = MetadataUpdateParams.builder(). key(SchemaMetadataKey.with("subject148", 42)). doc("doc doc doc doc doc doc doc doc doc"). appendAttribute("attr1", "attr1_value"). appendAttribute("attr2", 412). appendAttribute("attr3", Collections.singletonList("item123")). build(); String json = JsonMapper.toJson(origin); Assert.assertNotNull(json); MetadataUpdateParams deserialized = JsonMapper.jsonToObject(json, MetadataUpdateParams.class); Assert.assertNotNull(deserialized); Assert.assertEquals(origin, deserialized); }