Thank you Michael! This looks perfect but I have a `NoSuchMethodError` that I
cannot understand.
I am trying to implement a weighted shortest path algorithm from your `Spark
GraphX in Action` book. The part in question is Listing 6.4 "Executing the
shortest path algorithm that uses breadcrumbs
I have discovered that this dijkstra's function was written for scala 1.6. The
remainder of my code is 2.11.
I have checked the functions within the dijkstra function and can’t see any
that are illegal. For example `mapVertices`, `aggregateMessages` and
`outerJoinVertices` are all being used co