Write a function named collapse that accepts a list of integers as a parameter and returns a new list where each pair of integers from the original list has been replaced by the sum of that pair.
For example, if a list called a stores [7, 2, 8, 9, 4, 13, 7, 1, 9, 10], then the call of collapse(a) should return a new list containing [9, 17, 17, 8, 19].
The first pair from the original list is collapsed into 9 (7 + 2), the second pair is collapsed into 17 (8 + 9), and so on.
If the list stores an odd number of elements, the element is not collapsed.
For example, if the list had been [1, 2, 3, 4, 5], then the call would return [3, 7, 5].
Your function should not change the list that is passed as a parameter.
