docs: def best_fit(li, value):
      """For a sorted list li, returns the closest item to value"""
  
      index = min(bisect_left(li, value), len(li) - 1)
  
      if index in (0, len(li)):
          return index
  
      if li[index] - value < value - li[index-1]:
          return index
      else:
          return index-1