input: Write a function to print all the divisors of a given number. The function should take an integer as input and return a string listing all the divisors separated by commas.
  def print_divisors(num):
      divisors = []
      for i in range(1, num + 1):
          if num % i == 0:
              divisors.append(i)
      return ', '.join(map(str, divisors))
  
  assert print_divisors(12) == "1, 2, 3, 4, 6, 12"
  assert print_divisors(15) == "1, 3, 5, 15"
  assert print_divisors(0) == ""
  assert print_divisors(1) == "1"
  assert print_divisors(25) == "1, 5, 25"
output: def print_divisors(num):
      divisors = []
      for i in range(1, num + 1):
          if num % i == 0:
              divisors.append(i)
      return ', '.join(map(str, divisors))