Returns a list of checked indexes for this combobox.
        
        :return     [<int>, ..]

def checkedIndexes( self ):
        """
        Returns a list of checked indexes for this combobox.
        
        :return     [<int>, ..]
        """
        if ( not self.isCheckable() ):
            return []
        
        model  = self.model()
        return [i for i in range(self.count()) if model.item(i).checkState()]