Sorry. It does not work well. It will stop searching after meeting the upper-bound `prefix`

```scala
scala> var a = TreeMap("path/1"->1, "path/2"->2)
a: scala.collection.immutable.TreeMap[String,Int] = Map(path/1 -> 1, path/2 -> 2)

scala> a.from("path/").to("path/").keys
res8: Iterable[String] = Set()
```