code: def unquote_unreserved(uri):
      
      parts = uri.split('%')
      for i in range(1, len(parts)):
          h = parts[i][0:2]
          if len(h) == 2 and h.isalnum():
              try:
                  c = chr(int(h, 16))
              except ValueError:
                  raise ValueError("Invalid percent-escape sequence: '%s'" % h)
  
              if c in UNRESERVED_SET:
                  parts[i] = c + parts[i][2:]
              else:
                  parts[i] = '%' + parts[i]
          else:
              parts[i] = '%' + parts[i]
      return ''.join(parts)
docs: Un-escape any percent-escape sequences in a URI that are unreserved
      characters. This leaves all reserved, illegal and non-ASCII bytes encoded.
      :rtype: str