code: def b16decode(s, casefold=False):
      
      if casefold:
          s = s.upper()
      if re.search('[^0-9A-F]', s):
          raise TypeError('Non-base16 digit found')
      return binascii.unhexlify(s)
docs: Decode a Base16 encoded string.
  
      s is the string to decode.  Optional casefold is a flag specifying whether
      a lowercase alphabet is acceptable as input.  For security purposes, the
      default is False.
  
      The decoded string is returned.  A TypeError is raised if s is
      incorrectly padded or if there are non-alphabet characters present in the
      string.