void VariablesForm_KeyUp(object sender, KeyEventArgs keyEventArgs)
 {
     if (keyEventArgs.Control && keyEventArgs.KeyCode == Keys.S)
     {
         if (_isReadOnly)
         {
             UserInfoHandler.ShowInfo("File is in read-only mode.");
         }
         else
         {
             SaveChanges();
         }
     }
     if (keyEventArgs.Control && keyEventArgs.KeyCode == Keys.Z)
     {
         PerformAction(new VariablesUndoAction(_undoManager));
     }
     if (keyEventArgs.Control && keyEventArgs.KeyCode == Keys.Y)
     {
         PerformAction(new VariablesRedoAction(_undoManager));
     }
     if (treeAcronyms.Focused == true)
     {
         _acronymManager.HandleEnterKey(keyEventArgs);
     }
 }