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