Sets the current index as the checked index.
        
        :param      modelIndex | <QModelIndex>

def checkModelIndex( self, modelIndex ):
        """
        Sets the current index as the checked index.
        
        :param      modelIndex | <QModelIndex>
        """
        self.checkablePopup().hide()
        
        if not self.isCheckable():
            return
        
        self.setCheckedIndexes([modelIndex.row()])