create a sink stream, and start it later
return a pull-stream sink, that won't start reading until you say.
var delayed =var feed = d//create a pull stream, and direct to nowhere yet!//... later, start the sink.
pull.defer is a similar function, but it's a source instead of a sink.
create a fake sink stream, and then start it when you have the sink you want.
make a sink delay, and then allow it to start.