input: Write a function to calculate the running total of numbers in a given list using numpy. Return an array with the running totals. If the input list is empty, return an empty list.
  assert np.array_equal(runningTotal([1, 2, 3, 4]), np.array([1, 3, 6, 10]))
  assert np.array_equal(runningTotal([10, 15, 20]), np.array([10, 25, 45]))
  assert np.array_equal(runningTotal([0, -1, 1]), np.array([0, -1, 0]))
  assert np.array_equal(runningTotal([]), np.array([]))
  assert np.array_equal(runningTotal([5]), np.array([5]))
output: import numpy as np
  
  def runningTotal(lst):
      if not lst:
          return np.array([])
      return np.cumsum(lst)