Cumulative sum of numbers

Write a function named cumulative_sum_numbers that takes an integer n as input and returns the sum of all integers from 1 to n, inclusive. Use a for loop.

If n is less than 1, the range contains no integers and the returned sum is 0.

Complete the supplied function in Listing 1. Keep its signature and use the checks below it.

Listing 1: Starter function and supplied checks for cumulative sum of numbers.

def cumulative_sum_numbers(n: int) -> int:
    # Add code here!
    pass


assert cumulative_sum_numbers(5) == 15
assert cumulative_sum_numbers(10) == 55
assert cumulative_sum_numbers(1) == 1

Hint

range(start, stop) supplies integers beginning at start and ending before stop. For example, list(range(1, 4)) is [1, 2, 3]. An empty range supplies no values.

assert condition stops the check with an AssertionError when the condition is false.