input: Write a function to generate Fibonacci numbers using a recursive approach. The function should take an integer n as input and return the nth Fibonacci number. If n is 1 or 2, the function should return 1. Otherwise, it should return the sum of the two preceding Fibonacci numbers.
  
  Output:
  def fibonacci(n):
      if n == 1 or n == 2:
          return 1
      else:
          return fibonacci(n - 1) + fibonacci(n - 2)
  
  assert fibonacci(10) == 55
  assert fibonacci(1) == 1
  assert fibonacci(2) == 1
  assert fibonacci(7) == 13
  assert fibonacci(0) == None
output: def fibonacci(n):
      if n == 1 or n == 2:
          return 1
      else:
          return fibonacci(n - 1) + fibonacci(n - 2)