input: Write a function to generate an array with the running total of numbers in a given list using numpy. If the given list is empty then return an empty list.
  assert runningTotal([1, 2, 3, 4])==[1, 3, 6, 10]
  assert runningTotal([5, 10, 15, 20])==[5, 15, 30, 50]
  assert runningTotal([])==[]
output: import numpy as np
  
  def runningTotal(lst):
      if not lst:
          return []
      arr = np.array(lst)
      return np.cumsum(arr).tolist()