Subclassing cElementTree.XMLTreeBuilder

[mukappa]

I found an earlier post about subclassing cElementTree.Element which
can't
be done because it is a factory method.  I am trying to subclass
XMLTreeBuilder
with success using the python implementation, but not with
cElementTree.

[1013]$ python
Python 2.3.4 (#1, Feb 22 2005, 04:09:37)
[GCC 3.4.3 20041212 (Red Hat 3.4.3-9.EL4)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import elementtree.ElementTree
>>> class X(elementtree.ElementTree.XMLTreeBuilder):
...     pass
...
>>> import cElementTree
>>> class Y(cElementTree.XMLTreeBuilder):
...     pass
...
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: cannot create 'builtin_function_or_method' instances
>>>

Is it possible to subclass cElementTree.XMLTreeBuilder?

Thanks,
Mike