presto-hive/src/main/java/io/prestosql/plugin/hive/metastore/RecordingHiveMetastore.java/RecordingHiveMetastore/Pair
class RecordingHiveMetastore:        @JsonCreator
        public Pair(@JsonProperty("key") K key, @JsonProperty("value") V value)
        {
            this.key = requireNonNull(key, "key is null");
            this.value = requireNonNull(value, "value is null");
        }