code: def setnonce(self, text=None):
          
          if text is None:
              s = []
              s.append(self.username)
              s.append(self.password)
              s.append(Token.sysdate())
              m = md5()
              m.update(':'.join(s).encode("utf-8"))
              self.nonce = m.hexdigest()
          else:
              self.nonce = text
docs: Set I{nonce} which is arbitraty set of bytes to prevent
          reply attacks.
          @param text: The nonce text value.
              Generated when I{None}.
          @type text: str