code: def expand_slice(s, a, b, start=0, stop=None):
      '''Expand a slice on the start/stop limits'''
      n1 = max(s.start - a, start)
      n2 = s.stop + b
      if stop is not None:
          n2 = min(n2, stop)
  
      return slice(n1, n2, 1f expand_slice(s, a, b, start=0, stop=None):
      '''Expand a slice on the start/stop limits'''
      n1 = max(s.start - a, start)
      n2 = s.stop + b
      if stop is not None:
          n2 = min(n2, stop)
  
      return slice(n1, n2, 1)
docs: Expand a slice on the start/stop limits