old_contents: """Finding a sequence.
  
  Usage: sequencefinding.py NUMBERS...
  
  Arguments:
      NUMBERS   your sequence of numbers
  """
  
  import docopt
  
  
  def differences(a):
      return [t - s for s, t in zip(a, a[1:])]
  
  
  def constant_difference(a):
      if len(a) <= 1:
          return None
      if all(a[1] - a[0] == x for x in differences(a)):
          return a[1] - a[0]
      else:
          return None
  
  
  def linear_difference(a):
      depth = 1
      while len(a) > 0:
          cdiff = constant_difference(a)
          if cdiff is not None:
              return cdiff, depth
          a = differences(a)
          depth += 1
      return None
  
  args = docopt.docopt(__doc__)
  numbers = list(map(int, args['NUMBERS']))
  lin_diff = linear_difference(numbers)
  
  if lin_diff is not None:
      print("Found a linear difference of {} on layer {}.".format(*lin_diff))
  
new_contents: """Finding a sequence.
  
  Usage: sequencefinding.py NUMBERS...
  
  Arguments:
      NUMBERS   your sequence of numbers
  """
  
  import docopt
  
  
  def differences(a):
      return [t - s for s, t in zip(a, a[1:])]
  
  
  def constant_difference(a):
      if len(a) <= 1:
          return None
      if all(a[1] - a[0] == x for x in differences(a)):
          return a[1] - a[0]
      else:
          return None
  
  
  def linear_difference(a):
      depth = 1
      while len(a) > 0:
          cdiff = constant_difference(a)
          if cdiff is not None:
              return cdiff, depth
          a = differences(a)
          depth += 1
      return None
  
  args = docopt.docopt(__doc__)
  numbers = list(map(int, args['NUMBERS']))
  lin_diff = linear_difference(numbers)
  
  if lin_diff is not None:
      print("Found a linear difference of {} on layer {}.".format(*lin_diff))
  else:
      print("No sequence found.")
  
subject: Add fallback message when no sequence was found