docs: def unescape_string_literal(literal, encoding):
      r'''Unescape a string or unicode literal.
  
      Examples:
  
      >>> u = u'\u4e16\u754c\u4f60\u597d' # 世界你好
      >>> print unescape_string_literal(repr(u), 'utf-8')
      u'世界你好'
  
      >>> print unescape_string_literal(repr(u.encode('utf-8')), 'utf-8')
      '世界你好'
  
      >>> print unescape_string_literal(repr(u.encode('big5')), 'utf-8')
      '\xa5@\xac\xc9\xa7A\xa6n'
      '''
  
      if encoding is None:
          encoding = getfilesystemencoding()
  
      if literal[0] in 'uU':
  
          return literalize_string(
              literal[2:-1].decode('unicode-escape').encode(encoding),
              is_unicode=True
          )
  
      else:
  
          content = literal[1:-1].decode('string-escape')
  
          # keep it escaped if the encoding doesn't work on it
          try:
              content.decode(encoding)
          except UnicodeDecodeError:
              return literal
  
      return literalize_string(content)