I am getting the error TypeError: unsupported operand type(s) for +=: 'dict' and 'str' on this line of code : payload += "\x00" * (509 - len(payload)) the payload is: 'S\x96#:\x04\x04R\x1alD\x02\x04\x04V;\x15&\x06\x10 \x01' and what it should do is pad the payload until the length of the payload is 509 bytes long, but I do not understand this error, what does it mean and how can I solve it?