public Builder<K, V> addField(JsonField<K, V> field) {
            Objects.requireNonNull(field, "field");

            this.addField(field.name(), field.value());
            return this;
        }
@param nameMapper nameMapper does not guarantee uniqueness.
commons-server/src/main/java/com/navercorp/pinpoint/common/server/util/json/JsonFields.java