input: Write a function to debug the following Python code:
  
  ### Input:
  def f1 (x):
   y = x + 1
  def f2(x):
   return f1(x)*f1(x)
  
  f2(2)
  
  ### Output:
  # define f1 #
  def f1(x):
      return x + 1
  
  # define f2 #
  def f2(x):
      return f1(x) * f1(x)
  
  # call f2 #
  print(f2(2)) #Output: 9
output: def f1(x):
      return x + 1
  
  def f2(x):
      return f1(x) * f1(x)