将PCollection 组合成PCollection >的简单方法

I'm using Google Cloud Dataflow and have a ParDo function that requires access to all the elements in a PCollection. To accomplish this, I wanted to convert a PCollection<T> into a PCollection<Iterable<T>> containing a single Iterable of all the elements. I was wondering if there's a cleaner/simpler/faster solution to what I have come up with. I'm using Google Cloud Dataflow and have a ParD