code: def joinCommissioned(self, strPSKd='threadjpaketest', waitTime=20):
          
          print '%s call joinCommissioned' % self.port
          cmd = WPANCTL_CMD + 'joiner --start %s %s' %(strPSKd, self.provisioningUrl)
          print cmd
          if self.__sendCommand(cmd)[0] != "Fail":
              if self.__getJoinerState():
                  self.__sendCommand(WPANCTL_CMD + 'joiner --attach')
                  time.sleep(30)
                  return True
              else:
                  return False
          else:
              return False
docs: start joiner
  
          Args:
              strPSKd: Joiner's PSKd
  
          Returns:
              True: successful to start joiner
              False: fail to start joiner