   # returns). The sender (which is not responsible for replying to callers),
   # will store this request_id in the timeout store (this module's GenServer)
   # with a cast; since the caller blocks until the sender returns, we're sure
-  # that when the caller finishes then the timed out request id will have been
-  # *sent* (not received, because of the cast) to the timeout store.
+  # that when the caller finishes then the timed out request id will be stored.
   #
   # Now, everytime a response arrives from Redis to the receiver, the receiver
   # will check if the request_id for the corresponding request in its queue is

    end
  end

  def handle_cast({:add, request_id}, state) do
    {:noreply, HashSet.put(state, request_id)}
  end

  def handle_cast({:remove, request_id}, state) do

  end

  def add(pid, request_id) do
    GenServer.call(pid, {:add, request_id})
  end

  def remove(pid, request_id) do
