code: def set_username_ibm(self, username_ibm):
          
          if self.get_mode() == "ibm":
              self.__username_ibm = username_ibm
          else:
              raise Exception(
                  "Mode is {}, whereas it must be `ibm`".format(
                      self.get_moder()))
docs: Parameters
          ----------
          username_ibm : str
  
          Raises
          ------
          Exception
              If mode is not `ibm`