class OurCompany extends Plugin
{
    public function postLoad()
    {
        WidgetsList::add('OurCompany widgets', 'Banners', 'OurCompany', 'bannersGraph');
    }
}

class Controller extends \Piwik\Plugin\Controller
{
    public function bannersGraph()
    {
        $view = new View('@OurCompany/banners');
        $this->setPeriodVariablesView($view);
        $view->bannersGraph = $this->getBannersGraph(['page1', 'page2']);
        return $view->render();
    }

    public function getBannersGraph(array $defaultColumns = [])
    {
        $columns = Common::getRequestVar('columns', false);
        if (false !== $columns) {
            $columns = Piwik::getArrayFromApiParameter($columns);
        }

        $view = $this->getLastUnitGraphAcrossPlugins(
            $this->pluginName,
            __FUNCTION__,
            $columns,
            $defaultColumns,
            false,
            'OurCompany.getBannersEvolution'
        );
        $view->requestConfig->disable_generic_filters = true; // do not sort

        if (empty($view->config->columns_to_display) && !empty($defaultColumns)) {
            $view->config->columns_to_display = $defaultColumns;
        }

        return $this->renderView($view);
    }
}

class API extends \Piwik\Plugin\API
{
    public function getBannersEvolution($idSite, $period, $date, $segment = false)
    {
        $data = [/*...*/]; // sorted manually
        return DataTable::makeFromIndexedArray($data);
    }
}