@Override
    public String toString() {
      return MoreObjects.toStringHelper("Set").add("key", key)
          .add("value", value)
          .add("ifKey", ifKey)
          .add("ifType", ifType)
          .add("ifValue",ifValue)
          .add("ifKeyState", ifKeyState).omitNullValues().toString();
    }
A key/value pair to set in the type specified by {@link ConfigUpgradeChangeDefinition#configType}
ambari-server/src/main/java/org/apache/ambari/server/stack/upgrade/ConfigUpgradeChangeDefinition.java