How to focus the Editor after insert text?

I have a function to manipulate the editor by clicking a button in a toolWindow.

But after clicking, i want to refocus the editor. Has somebody an idea?

fun manipulateForElement(editor:Editor){

    val doc=editor.document
    val caret=editor.caretModel.primaryCaret
    val start=caret.selectionStart
    val end=caret.selectionEnd

     WriteCommandAction.runWriteCommandAction(editor.project) {
        doc.replaceString(start, end,"test string")

    }
    caret.removeSelection()
    caret.moveToOffset(start) // dont set the focus to the editor
}