code: def xy_reading_order(e1, e2):
      
      b1 = e1.bbox
      b2 = e2.bbox
      if round(b1[x0]) == round(b2[x0]):
          return float_cmp(b1[y0], b2[y0])
      return float_cmp(b1[x0], b2[x0])
docs: A comparator to sort bboxes from left to right, top to bottom