Modules
       groupbulk_to_next: convert GETBULK requests into GETNEXT requests for
           the handler.
           The only purpose of this handler is to convert a GETBULK request to
           a GETNEXT request.


       groupcache_handler: Maintains a cache of data for use by lower level
           handlers.
           This helper checks to see whether the data has been loaded
           'recently' (according to the timeout for that particular cache) and
           calls the registered 'load_cache' routine if necessary.


       groupdebug: print out debugging information about the handler chain
           being called.
           This is a useful module for run-time debugging of requests as the
           pass this handler in a calling chain.


       groupmode_end_call: at the end of a series of requests, call another
           handler hook.
           Handlers that want to loop through a series of requests and then
           receive a callback at the end of a particular MODE can use this
           helper to make this possible.


       groupmultiplexer: splits mode requests into calls to different
           handlers.
           The multiplexer helper lets you split the calling chain depending
           on the calling mode (get vs getnext vs set).


       groupread_only: make your handler read_only automatically
           The only purpose of this handler is to return an appropriate error
           for any requests passed to it in a SET mode.


       grouprow_merge: Calls sub handlers with request for one row at a time.
           This helper splits a whole bunch of requests into chunks based on
           the row index that they refer to, and passes all requests for a
           given row to the lower handlers.


       groupserialize: Calls sub handlers one request at a time.
           This functionally passes in one request at a time into lower
           handlers rather than a whole bunch of requests at once.