protected function get_column_tooltip($field)
    {
        $out = '';
        if ($this->column_tooltip && isset($this->column_tooltip[$field]))
        {
            $out .= ' ';
            $out .= $this->open_tag(array(
                'tag' => 'a',
                'href' => 'javascript:;',
                'class' => 'fruit-tooltip fruit-button-link',
                'title' => $this->column_tooltip[$field]['tooltip']));
            $out .= $this->open_tag(array('tag' => 'i', 'class' => ($this->column_tooltip[$field]['icon'] ? $this->column_tooltip[$field]['icon'] :
                    $this->theme_config('tooltip_icon'))));
            $out .= $this->close_tag('i');
            $out .= $this->close_tag('a');
        }
        return $out;
    }