input: 
  import numpy as np
  
  def runningTotal(arr):
      """Given a list of numbers, return an array with the running total of numbers.
      >>> runningTotal([1, 2, 3, 4])
      array([ 1,  3,  6, 10])
      >>> runningTotal([2, 4, 6, 8])
      array([ 2,  6, 12, 20])
      >>> runningTotal([5, 5, 5, 5])
      array([ 5, 10, 15, 20])
      """
      return np.cumsum(arr)
  
output:     return np.cumsum(arr)