input: Write a function to calculate the average of five numbers entered by a user. The function should prompt the user to enter five numbers one by one, then calculate and print the average of those numbers.
  assert calculate_average()==None
  assert calculate_average()==None
  assert calculate_average()==None
  assert calculate_average()==None
  assert calculate_average()==None
output: def calculate_average():
      total = 0
      for i in range(5):
          num = float(input("Enter a number: "))
          total += num
      average = total / 5
      print(average)