Comment 10 for bug 1394228

Unfortunately I've found that my solution doesn't work on arithmetic transformers applied to meters from different sources.
This is due to how a pipeline is defined.
A pipeline is a coupling between a (single) source and a sink. When a pipeline is flushed, only meters from the source "belonging" to the pipeline will be published.
So an arithmetic transformer defined on meters from different sources gives "Unable to perform calculation, not all of [...] are present"