How to get number of subscriptions

Is there a way to get the number of subscriptions?

For example

// Client
chatRoom = XXX
sub = instance.subscribe('chat', chatRoom)
Meteor.publish('chat', function(chat) { 
  cursor = Chats.find({
    chatRoom: chat
  return cursor

How would I get the number of subscriptions to the publication for each chatrooms?

Is there a native meteor way to do this?