input: Write a function to calculate the sum of each row in a 2D list.
  assert calculateRowSums([[1, 2, 3], [4, 5, 6]]) == [6, 15]
  assert calculateRowSums([[7, 8], [9, 10], [11, 12]]) == [15, 19, 23]
  assert calculateRowSums([[0, 0, 0], [1, 1, 1], [2, 2, 2]]) == [0, 3, 6]
output: def calculateRowSums(matrix):
      return [sum(row) for row in matrix]