input: Write a function to return an array with the running total of numbers in a given list using numpy. If the input list is empty, return an empty array.
  import numpy as np
  
  def runningTotal(arr):
      if len(arr) == 0:
          return np.array([])
      return np.cumsum(arr)
  
  assert np.array_equal(runningTotal([1, 2, 3, 4, 5]), np.array([1, 3, 6, 10, 15]))
  assert np.array_equal(runningTotal([5, 4, 3, 2, 1]), np.array([5, 9, 12, 14, 15]))
  assert np.array_equal(runningTotal([]), np.array([]))
  assert np.array_equal(runningTotal([-1, 0, 1]), np.array([-1, -1, 0]))
  assert np.array_equal(runningTotal([10]), np.array([10]))
output: import numpy as np
  
  def runningTotal(arr):
      if len(arr) == 0:
          return np.array([])
      return np.cumsum(arr)