input: import numpy as np
  
  def runningTotal(arr):
      """
      Return an array with the running total of numbers in a given list using numpy.
  
      >>> runningTotal([1, 2, 3, 4])
      array([ 1,  3,  6, 10])
      >>> runningTotal([5, -1, 2, 0])
      array([ 5,  4,  6,  6])
      >>> runningTotal([])
      array([], dtype=int32)
      """
      return np.cumsum(arr)
output:     return np.cumsum(arr)