input: 
  def runningTotal(arr):
      """ Given a list of numbers, return an array where each element is the running total of the numbers up to that point.
      >>> runningTotal([1, 2, 3])
      [1, 3, 6]
      >>> runningTotal([10, 20, 30, 40])
      [10, 30, 60, 100]
      """
      return np.cumsum(arr)
  
output:     running_total = []
      current_sum = 0
      for num in arr:
          current_sum += num
          running_total.append(current_sum)
      return running_total