code: def get_value(self, index):
          
          if index.column() == 0:
              return self.keys[ index.row() ]
          elif index.column() == 1:
              return self.types[ index.row() ]
          elif index.column() == 2:
              return self.sizes[ index.row() ]
          else:
              return self._data[ self.keys[index.row()] ]
docs: Return current value