Type mismatch in Task Graph examples

The Task Graph page http://www.scala-sbt.org/1.x/docs/Task-Graph.html contains three examples containing the expression ur.allConfigurations.take(3) which all seem broken:

$ cat build.sbt 
scalacOptions := {
  val ur = update.value  // update task happens-before scalacOptions
  val x = clean.value    // clean task happens-before scalacOptions
  // ---- scalacOptions begins here ----
  ur.allConfigurations.take(3)
}

$ sbt 
[info] Updated file /home/kelemen/temp/sbt-started/project/build.properties: set sbt.version to 1.0.2
[info] Loading project definition from /home/kelemen/temp/sbt-started/project
[info] Updating {file:/home/kelemen/temp/sbt-started/project/}sbt-started-build...
[info] Done updating.
/home/kelemen/temp/sbt-started/build.sbt:5: error: type mismatch;
 found   : scala.collection.immutable.Vector[sbt.librarymanagement.ConfigRef]
 required: Seq[String]
  ur.allConfigurations.take(3)
                           ^
[error] Type error in expression
Project loading failed: (r)etry, (q)uit, (l)ast, or (i)gnore? 

Open the Task Graph page and locate the three examples containing ur.allConfigurations.take(3). Check the expression's current type against the surrounding scalacOptions setting and identify the intended example value. Update all three examples so they are type-correct, then verify the shown build succeeds with sbt.