input: Write a function to shuffle a list of numbers. The function should return the shuffled list. If the input list is empty, return an empty list. Use Python's random.shuffle function to perform the shuffling.
  assert shuffle_list([1, 2, 3, 4, 5])==[3, 5, 2, 4, 1]
  assert shuffle_list([])==[]
  assert shuffle_list([7, 8, 9])==[9, 7, 8]
output: def shuffle_list(lst):
      if not lst:
          return []
      import random
      random.shuffle(lst)
      return lst