input: Write a function to implement the Fibonacci sequence. The function should take an integer n as input and return the nth Fibonacci number. If n is 0, the function should return 0. If n is 1, the function should return 1. For any other value of n, the function should return the sum of the two preceding Fibonacci numbers.
  def fibonacci_seq(n): 
      if n==0: 
          return 0
      elif n==1: 
          return 1
      else: 
          return fibonacci_seq(n-1)+fibonacci_seq(n-2)
  assert fibonacci_seq(0)==0
  assert fibonacci_seq(1)==1
  assert fibonacci_seq(5)==5
  assert fibonacci_seq(10)==55
output: def fibonacci_seq(n): 
      if n==0: 
          return 0
      elif n==1: 
          return 1
      else: 
          return fibonacci_seq(n-1)+fibonacci_seq(n-2)