Create a function called stringPractice$()$ that accepts a string. Your function should determine the $4$th and $5$th characters of that string and return it$.$ For example, stringPractice$(\text{'}$blackberries are great'$)$ would return the string ck$.$ You may assume the user will always pass a string that has at least $5$ characters in it$.$ You must use the slicing operator : to obtain the substring.