input: Write a function to reverse a given list. The function should return the reversed list.
  assert reverse_list([1,2, 3, 4, 5])==[5, 4, 3, 2, 1]
  assert reverse_list(['a', 'b', 'c'])==['c', 'b', 'a']
  assert reverse_list([1])==[1]
  assert reverse_list([])==[]
  assert reverse_list([10, 20, 30])==[30, 20, 10]
output: def reverse_list(lst):
      return lst[::-1]