renaming a node in a graph or pointed graph

[bblfish]

It does not seem easy to rename a node in a graph. This seems to be an operation that should be on a PointedGraph actually (or a PointedGraphW)

class PGwrapper[Rdf<:RDF](val pg: PointedGraph[Rdf]) extends AnyVal {
                 def rename(to: Rdf#Node): PointedGraph[Rdf] = ???
}

so for example say I create a PointedGraph from a PublicKey using the Cert PGBinder from the examples.

val keyPg = pub.toPG

this returns a PointedGraph, but with an anonymous node, where we would like a named node. So we'de like to rename that with

keyPg.rename(URI("#key"))

There are many other use cases where one may want to rename a node, eg: when one discoveres that people in one's foaf-profile no longer have a profile page, or if people who did not start having one.

[bblfish]

This works but is certainly not optimally efficient, as it has to iterate
through the whole graph.

implicit class PGwrapper(val pg: PointedGraph[Rdf]) extends AnyVal {
  def rename(to: Rdf#Node)(implicit ops: RDFOps[Rdf]): PointedGraph[Rdf] = {
    val oldNode = pg.pointer
    PointedGraph[Rdf](
      to,
      ops.makeGraph(pg.graph.triples.map{ triple =>
        ops.fromTriple(triple) match {
          case (oldNode,rel,obj) => ops.makeTriple(to,rel,obj)
          case (subj,rel,oldNode) => ops.makeTriple(subj,rel,to)
          case _ => triple
        }
      })
    )
  }
}

It could probably be optimised with RDFOps.find