input: Write a function to generate an array with the running total of numbers in a given list using numpy. The function should return the cumulative sum of the input array.
  import numpy as np
  
  def runningTotal(arr):
      return np.cumsum(arr)
  
  assert np.array_equal(runningTotal([1, 2, 3, 4]), np.array([1, 3, 6, 10]))
  assert np.array_equal(runningTotal([5, 10, 15]), np.array([5, 15, 30]))
  assert np.array_equal(runningTotal([0, -1, 2]), np.array([0, -1, 1]))
  assert np.array_equal(runningTotal([]), np.array([]))
  assert np.array_equal(runningTotal([1]), np.array([1]))
output: 
  def runningTotal(arr):
      return np.cumsum(arr)
  