docs: def decode(arg, delimiter=None, encodeseq=None):
      '''Decode a single argument from the file-system'''
      arg = coerce_unicode(arg, _c.FSQ_CHARSET)
      new_arg = sep = u''
      delimiter, encodeseq = delimiter_encodeseq(
          _c.FSQ_DELIMITER if delimiter is None else delimiter,
          _c.FSQ_ENCODE if encodeseq is None else encodeseq,
          _c.FSQ_CHARSET)
  
      # char-wise decode walk -- minimally stateful
      encoding_trg = sep
      for c in arg:
          if len(encoding_trg):
              encoding_trg = sep.join([encoding_trg, c])
              if 4 !=  len(encoding_trg):
                  continue
              try:
                  c = chr(int(encoding_trg, 16))
              except ValueError:
                  raise FSQEncodeError(errno.EINVAL, u'invalid decode'\
                                       u' target: {0}'.format(encoding_trg))
              c = coerce_unicode(c, _c.FSQ_CHARSET)
              encoding_trg = sep
          elif c == encodeseq:
              encoding_trg = u'0x'
              continue
  
          new_arg = sep.join([new_arg, c])
  
      # edge case, incomplete encoding at end of string
      if len(encoding_trg):
          raise FSQEncodeError(errno.EINVAL, u'truncated encoding at end of'
                               u' argument: {0}'.format(encoding_trg))
  
      return new_arg