src/Widgets/Bootstrap/Card.php
protected function renderHeaderImage() {
        if (!isset($this->headerImage)) {
            return '';
        }
        Html::addCssClass($this->headerImageOptions, ['widget' => 'card-img-top']);
        return $this->htmlHlp->img($this->headerImage, $this->headerImageOptions);
    }
protected function renderHeaderImage() {
        if (!isset($this->headerImage)) {
            return '';
        }
        Html::addCssClass($this->headerImageOptions, ['widget' => 'card-img-top']);
        return $this->htmlHlp->img($this->headerImage, $this->headerImageOptions);
    }
Render card top image
@return string