input: Write a function to calculate the average of five numbers entered by a user. The function should take no parameters, prompt the user to enter five numbers, calculate the average of those numbers, and then return the average.
  assert average_of_five()==sum([10, 15, 20, 25, 30])/5
  assert average_of_five()==sum([5, 5, 5, 5, 5])/5
  assert average_of_five()==sum([0, 0, 0, 0, 0])/5
  assert average_of_five()==sum([1, 2, 3, 4, 5])/5
  assert average_of_five()==sum([100, 200, 300, 400, 500])/5
output: def average_of_five():
      numbers = []
      for i in range(5):
          num = float(input("Enter a number: "))
          numbers.append(num)
      return sum(numbers) / 5