# File lib/nats/client.rb, line 528
  def unsubscribe(sid, opt_max=nil)
    return if draining?
    opt_max_str = " #{opt_max}" unless opt_max.nil?
    send_command("UNSUB #{sid}#{opt_max_str}#{CR_LF}")
    return unless sub = @subs[sid]
    sub[:max] = opt_max
    @subs.delete(sid) unless (sub[:max] && (sub[:received] < sub[:max]))
  end