input: 
  def is_prime(num: int) -> str:
      """Determines if the given number is prime.
      >>> is_prime(17)
      '17 is a prime number.'
      >>> is_prime(8)
      '8 is not a prime number.'
      """
      
      if num < 2:
          return f"{num} is not a prime number."
      
      for i in range(2, int(num ** 0.5) + 1):
          if num % i == 0:
              return f"{num} is not a prime number."
      
      return f"{num} is a prime number."
  
output:     if num < 2:
          return f"{num} is not a prime number."
      
      for i in range(2, int(num ** 0.5) + 1):
          if num % i == 0:
              return f"{num} is not a prime number."
      
      return f"{num} is a prime number."