code: public UNode toDoc() {
          // Root node is map with 1 child per result field and optionally "docs".
          UNode result = UNode.createMapNode("batch-result");
          for (String fieldName : m_resultFields.keySet()) {
              result.addValueNode(fieldName, m_resultFields.get(fieldName));
          }
          if (m_objResultList.size() > 0) {
              UNode docsNode = result.addArrayNode("docs");
              for (ObjectResult objResult : m_objResultList) {
                  docsNode.addChildNode(objResult.toDoc());
              }
          }
          return result;
      }
docs: Serialize this BatchResult result into a UNode tree. The root node is called
  "batch-result".
  
  @return  This object serialized into a UNode tree.