feat(docs): type fix - apply pep8 by using docstring instead of comment in the doc. (#135181)

Giving the right example incitates the tutorial readers to do the same in the future.

Doc/tutorial/modules.rst

@@ -27,14 +27,16 @@ called :file:`fibo.py` in the current directory with the following contents::
 
    # Fibonacci numbers module
 
-   def fib(n):    # write Fibonacci series up to n
+   def fib(n):
+       """Write Fibonacci series up to n."""
        a, b = 0, 1
        while a < n:
            print(a, end=' ')
            a, b = b, a+b
        print()
 
-   def fib2(n):   # return Fibonacci series up to n
+   def fib2(n):
+       """Return Fibonacci series up to n."""
        result = []
        a, b = 0, 1
        while a < n: