'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.'

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)
