input: Write a function to calculate the running total of numbers in a given list using numpy. The function should return an array with the cumulative sum of the input list. If the input list is empty, it 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([7, 3, 2, 8]), np.array([7, 10, 12, 20]))
output: import numpy as np
  
  def runningTotal(lst):
      if not lst:
          return np.array([])
      return np.cumsum(lst)