code: def iter_child_nodes(self, exclude=None, only=None):
          
          for field, item in self.iter_fields(exclude, only):
              if isinstance(item, list):
                  for n in item:
                      if isinstance(n, Node):
                          yield n
              elif isinstance(item, Node):
                  yield item
docs: Iterates over all direct child nodes of the node.  This iterates
          over all fields and yields the values of they are nodes.  If the value
          of a field is a list all the nodes in that list are returned.