'Process pick event
each child artist will fire a pick event if *mouseevent* is over
the artist and the artist has picker set'

def pick(self, mouseevent):

    if self.pickable():
        picker = self.get_picker()
        if callable(picker):
            (inside, prop) = picker(self, mouseevent)
        else:
            (inside, prop) = self.contains(mouseevent)
        if inside:
            self.figure.canvas.pick_event(mouseevent, self, **prop)
    for a in self.get_children():
        ax = getattr(a, u'axes', None)
        if ((mouseevent.inaxes is None) or (ax is None) or (mouseevent.inaxes == ax)):
            a.pick(mouseevent)
