PUBSUB <subcommand> [<arg> [value] [opt] ...]. Subcommands are:
CHANNELS [<pattern>]
    Return the currently active channels matching a <pattern> (default: '*').
NUMPAT
    Return number of subscriptions to patterns.
NUMSUB [<channel> ...]
    Return the number of subscribers for the specified channels, excluding
    pattern subscriptions(default: no channels).
HELP
    Prints this help.
