input: Write a python function to reverse a string and print each character on a new line.
  assert reverse_string("Hello, World!") == "!dlroW ,olleH"
  assert reverse_string("Python") == "nohtyP"
  assert reverse_string("12345") == "54321"
output: def reverse_string(s):
      reversed_s = s[::-1]
      for char in reversed_s:
          print(char)
      return reversed_s