input: Write a python function to encode a string by shifting each character by one and another function to decode it by shifting each character back by one.
  assert encodeString("hello") == "ifmmp"
  assert encodeString("abc") == "bcd"
  assert decodeString("ifmmp") == "hello"
  assert decodeString("bcd") == "abc"
output: def encodeString(s):
      return ''.join(chr(ord(c) + 1) for c in s)
  
  def decodeString(s):
      return ''.join(chr(ord(c) - 1) for c in s)