Naive Fibonacci

Write fib(n: int) -> int that returns the nth Fibonacci number by plain recursion: fib(0) is 0, fib(1) is 1, and every later number is the sum of the two numbers before it, so the sequence runs 0, 1, 1, 2, 3, 5, 8. Write a base case for n below 2 and one recursive case that calls the function twice. This naive version repeats the same work many times over, so it gets slow quickly; the tests keep n at 20 or below. Do NOT write a main block or any top-level test code; the tests construct the calls. Input: one integer n, no prompt, which the tests read and pass to your function before printing the value it returns.