input: Write a python function to encode a string such that each character is replaced by its corresponding character from the end of the alphabet and then decode it back to the original string.
  assert encoding("hello") == "svool"
  assert decoding("svool") == "hello"
  assert encoding("world") == "dliow"
  assert decoding("dliow") == "world"
  assert encoding("python") == "kbgsli"
  assert decoding("kbgsli") == "python"
output: def encode_char(c):
      if 'a' <= c <= 'z':
          return chr(ord('z') - (ord(c) - ord('a')))
      elif 'A' <= c <= 'Z':
          return chr(ord('Z') - (ord(c) - ord('A')))
      return c
  
  def decode_char(c):
      return encode_char(c)
  
  def encoding(s):
      return ''.join(encode_char(c) for c in s)
  
  def decoding(s):
      return ''.join(decode_char(c) for c in s)