input: Write a function to create a Python code that returns an array with the running total of numbers in a given list using numpy. The function should take a list as input, compute the running total using numpy's cumsum function, and return the resultant array. If the given list is empty, the function should return an empty list.
  
  import numpy as np
  
  def runningTotal(arr):
      return np.cumsum(arr)
  
  
  
  assert list(runningTotal([1, 2, 3, 4]))==[1, 3, 6, 10]
  assert list(runningTotal([5, 10, 15, 20]))==[5, 15, 30, 50]
  assert list(runningTotal([1]))==[1]
  assert list(runningTotal([]))==[]
  
output: import numpy as np
  
  def runningTotal(arr):
      if not arr:
          return []
      return np.cumsum(arr)