input: Write a function to determine if a given number is prime and then print all prime numbers up to a given limit \( n \). The function should iterate from 2 to \( n \) and use the prime-checking logic to print each prime number. If the input limit \( n \) is less than or equal to 1, the function should return a message indicating no prime numbers are found.
  
  def print_primes(n):
      if n <= 1:
          return "No prime numbers found."
      
      def is_prime(num):
          for i in range(2, int(num ** 0.5) + 1):
              if num % i == 0:
                  return False
          return True
      
      primes = []
      for num in range(2, n + 1):
          if is_prime(num):
              primes.append(num)
      
      return primes
  
  assert print_primes(10) == [2, 3, 5, 7]
  assert print_primes(1) == "No prime numbers found."
  assert print_primes(0) == "No prime numbers found."
  assert print_primes(20) == [2, 3, 5, 7, 11, 13, 17, 19]
  assert print_primes(15) == [2, 3, 5, 7, 11, 13]
output: def print_primes(n):
      if n <= 1:
          return "No prime numbers found."
      
      def is_prime(num):
          for i in range(2, int(num ** 0.5) + 1):
              if num % i == 0:
                  return False
          return True
      
      primes = []
      for num in range(2, n + 1):
          if is_prime(num):
              primes.append(num)
      
      return primes