'debug' command is birdc

Hello, Would someone be so kind to explain the syntax of 'debug' command in birdc? The description in User's Guide is very short. I need to debug a filtering to/from certain BGP neighbor. I've tried different options: bird> debug ? debug (<protocol> | <pattern> | all) (all | off | { states | routes | filters | interfaces | events | packets }) Control protocol debugging via BIRD logs bird> debug FREEBIT filters syntax error bird> debug BGP filters syntax error bird> debug bgp filters syntax error bird> debug all filters syntax error bird> debug all states syntax error Thanks in advance! -- MINO-RIPE