input: Write a python function to separate characters and numbers from a string.
  assert separate_charnum("ab12cd3") == (['a', 'b', 'c', 'd'], [1, 2, 3])
  assert separate_charnum("x9y8z7") == (['x', 'y', 'z'], [9, 8, 7])
  assert separate_charnum("123abc") == (['a', 'b', 'c'], [1, 2, 3])
output: def separate_charnum(s):
      chars = []
      nums = []
      for char in s:
          if char.isdigit():
              nums.append(int(char))
          else:
              chars.append(char)
      return chars, nums