Return current value

def get_value(self, index):
        """Return current value"""
        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()] ]