In the following, dir(Node) should include the name 'z', and Node.z
should be 'Node'. However, dir(Node) does not include 'z', and Node.z is
undefined (AttributeError). This is directly contrary to the Python
documentation, which says "metaclasses can modify dict".

class MetaNode(type):
    def __init__(cls, name, bases, cdict):
        cdict['z'] = name
        type.__init__(name, bases, cdict)
class Node(object):
    __metaclass__ = MetaNode

print dir(Node)
print Node.z