input: Write a function to return an array with the running total of numbers in a given list using numpy. The function should take a list as input and return an array where each element is the cumulative sum of the elements up to that index in the input list. If the input list is empty, the function should return an empty array.
  import numpy as np
  
  def runningTotal(arr):
      return np.cumsum(arr)
  
  assert np.array_equal(runningTotal([1, 2, 3, 4]), [1, 3, 6, 10])
  assert np.array_equal(runningTotal([5, 10, 15]), [5, 15, 30])
  assert np.array_equal(runningTotal([]), [])
  assert np.array_equal(runningTotal([-1, 0, 1, 0]), [-1, -1, 0, 0])
  assert np.array_equal(runningTotal([10]), [10])
output: import numpy as np
  
  def runningTotal(arr):
      return np.cumsum(arr)