protected function getColumnDataCellContent($column, $model, $key, $index)
    {
        if ($column->content === null) {
            return $this->formatter->format($this->getColumnDataCellValue($column, $model, $key, $index), $column->format);
        } else {
            if ($column->content !== null) {
                return call_user_func($column->content, $model, $key, $index, $column);
            } else {
                return $this->emptyCell;
            }
        }
    }