code: def set_subsystem_handler(self, name, handler, *larg, **kwarg):
          
          try:
              self.lock.acquire()
              self.subsystem_table[name] = (handler, larg, kwarg)
          finally:
              self.lock.release()
docs: Set the handler class for a subsystem in server mode.  If a request
          for this subsystem is made on an open ssh channel later, this handler
          will be constructed and called -- see `.SubsystemHandler` for more
          detailed documentation.
  
          Any extra parameters (including keyword arguments) are saved and
          passed to the `.SubsystemHandler` constructor later.
  
          :param str name: name of the subsystem.
          :param handler:
              subclass of `.SubsystemHandler` that handles this subsystem.