input: Write a function that takes an integer input from the user and prints its cube. The function should prompt the user to enter a number, then calculate and print the cube of that number.
  
  assert cube_number()
  assert cube_number()
  assert cube_number()
  assert cube_number()
  
  Note: The function `cube_number` does not take any parameters and directly interacts with the user to get the input. The assert statements are placeholders and will not have expected values since the function interacts with user input during runtime.
output: def cube_number():
      number = int(input("Enter a number: "))
      print(number ** 3)