_ABCTree still has vestiges of being a dict

[nedbat]

One of my tests had this failure (among others):

AttributeError("'RBTree' object has no attribute 'items'") raised in repr()

which is due to _ABCTree.__repr__:

    def __repr__(self):
        """T.__repr__(...) <==> repr(x)"""
        tpl = "%s({%s})" % (self.__class__.__name__, '%s')
        return tpl % ", ".join(("%r: %r" % item for item in self.items()))

Also, I notice in _ABCTree.__init__:

        if items is not None:
            self.update(items)

but there is no update method.