input: Write a function to generate Fibonacci numbers recursively in Python. 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. For any other value of `n`, the function should return the sum of the two preceding Fibonacci numbers. The function should be named `fibonacci`.
  assert fibonacci(1)==1
  assert fibonacci(2)==1
  assert fibonacci(10)==55
  assert fibonacci(15)==610
  assert fibonacci(1)==1
output: def fibonacci(n):
      if n == 1 or n == 2:
          return 1
      else:
          return fibonacci(n-1) + fibonacci(n-2)