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