__subclasses__

[James Rowe]

A search for __subclasses__ on the www.python.org
documentation search pages turns up empty. I can
find not mention of it in my Python books or even
in the "What's new in Python 2.2" document.  But:

class Foo(object):
    def __init__(self):
        object.__init__(self)

class Bar(Foo):
	pass

dir(Foo) # returns:

 ['__class__', '__delattr__', '__dict__', '__doc__',
 '__getattribute__', '__hash__', '__init__', '__module__',
 '__new__', '__reduce__', '__repr__', '__setattr__',
 '__str__', '__weakref__']

But there is a __subclasses__ method:

Foo.__subclasses__() # returns:

 [<class '__main__.Bar'>]


So I suppose the question is: Why is __subclasses__ not documented
or listed?  Can we safely use __subclasses__ and not worry about
it "going away" in the future?