code: def getIndexGrid(self, name):
          
          index_map = self.mapTableFile.indexMaps.filter_by(name=name).one()
  
          gssha_pro_card = self.getCard("#PROJECTION_FILE")
          if gssha_pro_card is None:
              raise ValueError("#PROJECTION_FILE card not found ...")
  
          with tmp_chdir(self.project_directory):
              # return gssha grid
              return GDALGrid(index_map.filename,
                              gssha_pro_card.value.strip('"').strip("'"))
docs: Returns GDALGrid object of index map
  
          Paramters:
              name(str): Name of index map in 'cmt' file.
  
          Returns:
              GDALGrid