input: 
  import numpy as np
  
  def runningTotal(arr):
      """ Return an array with the running total of numbers in a given list.
      >>> runningTotal([1, 2, 3, 4])
      array([ 1,  3,  6, 10])
      >>> runningTotal([0, -1, 1, -2])
      array([ 0, -1,  0, -2])
      """
      return np.cumsum(arr)
  
output:     return np.cumsum(arr)