'Return a tuple of ``(key, axes)`` for the active axes.
If no axes exists on the stack, then returns ``(None, None)``.'

def current_key_axes(self):

    if (not len(self._elements)):
        return (self._default, self._default)
    else:
        (key, (index, axes)) = self._elements[self._pos]
        return (key, axes)
