protected function show_hide_link($column, $index) {
        if ($index > 0 || !$this->hasgrade) {
            return parent::show_hide_link($column, $index);
        }
        return '';
    }
protected function show_hide_link($column, $index) {
        if ($index > 0 || !$this->hasgrade) {
            return parent::show_hide_link($column, $index);
        }
        return '';
    }
protected function show_hide_link ( $ column , $ index ) { if ( $ index > 0 || ! $ this -> hasgrade ) { return parent :: show_hide_link ( $ column , $ index ) ; } return '' ; }
Override the table show_hide_link to not show for select column.

@param string $column the column name, index into various names.
@param int $index numerical index of the column.
@return string HTML fragment.
Override the table show_hide_link to not show for select column .