'Sort by axis displacement, which allows us to figure out which parts
of labels to not repeat.'

def sort(self):

    for axis in self.world:
        self.world[axis] = sort_using(self.world[axis], self.disp[axis])
        self.pixel[axis] = sort_using(self.pixel[axis], self.disp[axis])
        self.angle[axis] = sort_using(self.angle[axis], self.disp[axis])
        self.text[axis] = sort_using(self.text[axis], self.disp[axis])
        self.disp[axis] = sort_using(self.disp[axis], self.disp[axis])
