if !ok {
			return Help{}, config.Errorf("unknown sub-system %s", subSys)
		}
	}

	h, ok := config.HelpSubSysMap[subSys]
	if !ok {
		return Help{}, config.Errorf("unknown sub-system %s", subSys)
	}
	if key != "" {
		value, ok := h.Lookup(key)
		if !ok {
			return Help{}, config.Errorf("unknown key %s for sub-system %s",
				key, subSys)
		}
		h = config.HelpKVS{value}
	}