Question $2\mathrm{.}0$

Write a function Sum$(n)$ that takes a non$-$negative integer $(n)$ and returns the sum of its digits $($digit$\_$sum $)$ as an integer. If $n$ is negative and$/$or non$-$integer, the

function should return "Invalid Input." Be careful with your string formatting. Minor differences will result in a failed test.

Test your Sum$(n)$ function for $n=200500$ in the following cell. Assign the output to $q_0^2.$ Feel free to try it for other inputs.

Hint: Strings are iterable.

Examples:$11245$'Invalid Input.$\text{'}\text{'}$Invalid Input.$\text{'}$a

$6$