python类collections()的实例源码

def _remove_all_artists(self):
        for value in self._mplot_objects.values():
            # String is a sequence too, but it will not be here
            if isinstance(value, collections.Sequence):
                for obj in value:
                    if obj:
                        obj.remove()  
            else:
                if value:
                    value.remove()
        self._mplot_objects = {}