def set_subsystem_handler(self, name, handler, *larg, **kwarg):
try:<EOL><INDENT>self.lock.acquire()<EOL>self.subsystem_table[name] = (handler, larg, kwarg)<EOL><DEDENT>finally:<EOL><INDENT>self.lock.release()<EOL><DEDENT>
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 L{SubsystemHandler} for more
detailed documentation.

Any extra parameters (including keyword arguments) are saved and
passed to the L{SubsystemHandler} constructor later.

@param name: name of the subsystem.
@type name: str
@param handler: subclass of L{SubsystemHandler} that handles this
    subsystem.
@type handler: class