docs: def clip_slices(r, region, scale=1):
      '''Intersect slices with a region.'''
      t = []
      for ch in r:
          a1 = intersection(ch[0], region[0], scale=scale)
          if a1 is None:
              continue
          a2 = intersection(ch[1], region[1], scale=scale)
          if a2 is None:
              continue
  
          t.append((a1, a2))
  
      return t