Write a function called count$\_$vowels $(s)$ that takes in a string $s$ as an argument and returns the number of vowels in the string. Use a for loop and an if statement to check if eachtcharacter in the string is a vowel.

Test case:

print$($count$\_$vowels$("$hello$"))$ # Output: $2$

print$($count$\_$vowels$("$Python$"))$ # Output: $2$

print$($count$\_$vowels$("$The quick brown fox jumps over the lazy dog"$))$ # Output: $12$

print$($count$\_$vowels$("\text{'}"))$ # Output: $0$