code: public int getFirstChild(int nodeHandle)
    {
  
      int identity = makeNodeIdentity(nodeHandle);
      int firstChild = _firstch(identity);
  
      return makeNodeHandle(firstChild);
    }
docs: Given a node handle, get the handle of the node's first child.
  If not yet resolved, waits for more nodes to be added to the document and
  tries again.
  
  @param nodeHandle int Handle of the node.
  @return int DTM node-number of first child, or DTM.NULL to indicate none exists.