code: def overhang(self, tile):
          
          ll = np.abs(amin(self.l - tile.l, aN(0, dim=self.dim)))
          rr = np.abs(amax(self.r - tile.r, aN(0, dim=self.dim)))
          return ll, rr
docs: Get the left and right absolute overflow -- the amount of box
          overhanging `tile`, can be viewed as self \\ tile (set theory relative
          complement, but in a bounding sense)