code: function psubscribe(conn, channels) {
    return this.doSubscribe(
      PUBSUB.PSUBSCRIBE,
      PUBSUB.PATTERNS,
      this._patterns, conn, channels);
  }
docs: /*
  Subscribe to pattern channel(s).
  
  It is expected that the command handler has validated
  the command arguments.
  
  @param conn The client connection.
  @param channels Array of channels.