input: Write a function to return an array with the running total of numbers in a given list using numpy's cumsum function. The given list should be passed as an argument to the function. If the given array is empty then 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, 20]), [5, 15, 30, 50])
  assert np.array_equal(runningTotal([]), [])
  assert np.array_equal(runningTotal([-1, -2, -3, -4]), [-1, -3, -6, -10])
output: import numpy as np
  
  def runningTotal(arr):
      return np.cumsum(arr)