input: Write a function that takes a string as input and prints all of its substrings in order from longest to shortest length.
  
  def substring_in_order(string): 
      result = [] 
      n = len(string) 
      for l in range(n, 0, -1): 
          for i in range(n-l + 1): 
              result.append(string[i:i+l]) 
      return result 
  
  assert substring_in_order("abc") == ["abc", "ab", "bc", "a", "b", "c"]
  assert substring_in_order("xy") == ["xy", "x", "y"]
  assert substring_in_order("a") == ["a"]
  assert substring_in_order("") == []
output: def substring_in_order(string): 
      result = [] 
      n = len(string) 
      for l in range(n, 0, -1): 
          for i in range(n-l + 1): 
              result.append(string[i:i+l]) 
      return result