nums has only one element. If so, return that element as the triangular sum.nums is greater than 1:
a. Initialize an empty list newNums.
b. Iterate over nums from the first element to the second-to-last element.
c. For each iteration, calculate the sum of the current element and the next element modulo 10 and append it to newNums.
d. Replace nums with newNums.nums, which is the triangular sum.