code: public int getNextAttribute(int nodeHandle) {
      int nodeID = makeNodeIdentity(nodeHandle);
  
      if (_type(nodeID) == DTM.ATTRIBUTE_NODE) {
        return makeNodeHandle(getNextAttributeIdentity(nodeID));
      }
  
      return DTM.NULL;
    }
docs: Given a node handle, advance to the next attribute.
  If an attr, we advance to
  the next attr on the same node.  If not an attribute, we return NULL.
  
  @param nodeHandle int Handle of the node.
  @return int DTM node-number of the resolved attr,
  or DTM.NULL to indicate none exists.