input: Write a function to reverse a list.
  
  def reverse_list(list): 
      return list[::-1]
  
  assert reverse_list([1,2,3,4,5])==[5,4,3,2,1]
  assert reverse_list([1])==[1]
  assert reverse_list([])==[]
  assert reverse_list([10, 20, 30])==[30, 20, 10]
output: def reverse_list(list): 
      return list[::-1]