code: private void leafFieldtoDoc(UNode parentNode, String fieldName) {
          assert parentNode != null;
          
          Set<String> addSet = null;
          if (m_valueMap.containsKey(fieldName)) {
              addSet = new TreeSet<String>(m_valueMap.get(fieldName));
          }
          List<String> removeSet = m_valueRemoveMap.get(fieldName);
          if (addSet != null && addSet.size() == 1 && removeSet == null) {
              parentNode.addValueNode(fieldName, addSet.iterator().next(), "field");
          } else {
              UNode fieldNode = parentNode.addMapNode(fieldName, "field");
              if (addSet != null && addSet.size() > 0) {
                  UNode addNode = fieldNode.addArrayNode("add");
                  for (String value : addSet) {
                      addNode.addValueNode("value", value);
                  }
              }
              if (removeSet != null && removeSet.size() > 0) {
                  UNode addNode = fieldNode.addArrayNode("remove");
                  for (String value : removeSet) {
                      addNode.addValueNode("value", value);
                  }
              }
          }
      }
docs: parent node.