Lab Coat Challenge 6: Quick Mode

Hey there dev's and dev's-to-be! We have a 'Quick' Lab Coat Challenge for you. Review the challenge, take a look at the starter code, and then give it your best shot. Get the right answer and earn your Lab Coat Badge.

You must use the following code and can only add to the code provided below.

/*  LAB COAT CHALLENGE: What is the minimum amount of lines
needed in order to find the mode of the following list
of integers? */

//  lists of integers to be used in the asserts
list<Integer> numbers1 = new list<Integer> {2,5,1,2,7,1,2,6,4,6,2,3,8,9};
list<Integer> numbers2 = new list<Integer> {2,5,1,6,7,8,1,5};
list<Integer> numbers3 = new list<Integer> {5,4,7,1,7,2,3,5,4};
list<Integer> numbers4 = new list<Integer> {5,4,7,2,1,7,1,2,5,4};

//  Test your code
system.assertEquals(mode(numbers1), new set<Integer> {2});
system.assertEquals(mode(numbers2), new set<Integer> {1,5});
system.assertEquals(mode(numbers3), new set<Integer> {4,5,7});
system.assertEquals(mode(numbers4), new set<Integer>());

//  YOUR CHANGES START BELOW

//   Implement the following method
set<Integer> mode(list<Integer> listOfIntegersToTest) {
set<Integer> returnValues = new set<Integer>();

// Your code here

return returnValues;

}