Create a method named isSorted. isSorted accepts a list of OurComparables and returns true if the list is sorted in ascending order and false otherwise. If the passed list is empty you should throw an IllegalArgumentException.

As a reminder, compareTo returns a negative integer, zero, or a positive integer as this object is less than, equal to, or greater than the passed object. OurComparable works exactly the same as the official Comparable interface, except it is slightly simplified and does not accept a type parameter.