def unreachable(self, completed, failed=None):
        if len(self) == 0:
            return False
        against = set()
        if not self.success:
            against = completed
        if failed is not None and not self.failure:
            against = against.union(failed)
        if self.all:
            return not self.isdisjoint(against)
        else:
            return self.issubset(against)
Find and return the scroll widget child for this widget.
dataset/ETHPy150Open ipython/ipython-py3k/IPython/parallel/controller/dependency.py/Dependency.unreachable--crossover with--dataset/ETHPy150Open ContinuumIO/ashiba/enaml/enaml/wx/wx_scroll_area.py/WxScrollArea.scroll_widget