input: Write a function to calculate the cubic values of a given list of numbers from 1 to 8 and print each result. If the list is not provided, return None.
  def calculate_cubics(num_list):
      if not num_list:
          return None
      for num in num_list:
          print(num**3)
  
  assert calculate_cubics([1, 2, 3, 4, 5, 6, 7, 8])==None
  assert calculate_cubics([])==None
output: def calculate_cubics(num_list):
      if not num_list:
          return None
      for num in num_list:
          print(num**3)