def getFileDialogFilter(self):
        """ Returns a filter that can be used in open file dialogs,
            for example: 'All files (*);;Txt (*.txt;*.text);;netCDF(*.nc;*.nc4)'
        """
        filters = []
        for regRti in self.items:
            filters.append(regRti.getFileDialogFilter())
        return ';;'.join(filters)