input: Write a function to return an array with the running total of numbers in a given list using numpy. If the given list is empty, return an empty array.
  assert runningTotal([1, 2, 3, 4])==[1, 3, 6, 10]
  assert runningTotal([10, 20, 30])==[10, 30, 60]
  assert runningTotal([5])==[5]
  assert runningTotal([])==[]
output: import numpy as np
  
  def runningTotal(lst):
      if not lst:
          return np.array([])
      return np.cumsum(lst)