input: Write a function to implement a recursive Python function to generate Fibonacci numbers. The function should return the nth Fibonacci number. If n is 1 or 2, the function should return 1. For other values of n, the function should return the sum of the two preceding Fibonacci numbers.
  assert fibonacci(1)==1
  assert fibonacci(2)==1
  assert fibonacci(5)==5
  assert fibonacci(10)==55
output: def fibonacci(n):
      if n == 1 or n == 2:
          return 1
      else:
          return fibonacci(n-1) + fibonacci(n-2)