Add AssertionException, specialize pprint
diff --git a/ide/CellModel.h b/ide/CellModel.h
index 1f56056..428422a 100644
--- a/ide/CellModel.h
+++ b/ide/CellModel.h
@@ -44,6 +44,8 @@
     Q_INVOKABLE void addCell(const Cell &cell);
     Q_INVOKABLE void addCell(QString code, QString result);
 
+    Q_INVOKABLE void insertCellBefore(int index);
+
 private:
     Notebook *_notebook;
     void announceCellChange(Cell *cell, int role);