input: Write a python function to print all prime numbers less than a given number.
  assert print_prime_numbers(10) == "2\n3\n5\n7\n"
  assert print_prime_numbers(20) == "2\n3\n5\n7\n11\n13\n17\n19\n"
  assert print_prime_numbers(5) == "2\n3\n"
output: def print_prime_numbers(n):
      def is_prime(k):
          if k <= 1:
              return False
          for i in range(2, int(k ** 0.5) + 1):
              if k % i == 0:
                  return False
          return True
  
      primes = []
      for num in range(2, n):
          if is_prime(num):
              primes.append(str(num))
      return "\n".join(primes) + "\n"