Magento 2 Add extension attribute in product list

I want to add extra data in product list rest api using extension attribute via Plugin in Magento 2 but it's not working.

> Uncaught TypeError: Argument 2 passed to
> Vendor\ModuleName\Plugin\ProductPlugin::afterGetList() must be an
> instance of Magento\Catalog\Api\Data\ProductSearchResultsInterface,
> instance of Magento\Framework\Api\SearchResults given

extension_attribute.xml

<extension_attributes for="Magento\Catalog\Api\Data\ProductInterface">
    <attribute code="seller" type="Magento\Catalog\Api\Data\CustomOptionInterface[]" />
</extension_attributes>

di.xml

<type name="Magento\Catalog\Api\ProductRepositoryInterface">
    <plugin name="add_more_info_in_product" type="Vendor\ModuleName\Plugin\ProductPlugin" sortOrder="15" />
</type>

Vendor\ModuleName\Plugin\ProductPlugin.php

use Magento\Catalog\Api\Data\ProductInterface;

class ProductPlugin
{
    protected $productExtensionFactory;
    protected $productFactory;

    public function __construct(
        \Magento\Catalog\Api\Data\ProductExtensionFactory $productExtensionFactory,
        \Magento\Catalog\Model\ProductFactory $productFactory
    )
    {
        $this->productFactory = $productFactory;
        $this->productExtensionFactory = $productExtensionFactory;
    }

    public function afterGet(
        \Magento\Catalog\Api\ProductRepositoryInterface $subject,
        \Magento\Catalog\Api\Data\ProductInterface $entity
    )
    {
        /** @var ProductInterface $product */
        $product = $entity;
        // Fetch the raw product model (I have not found a better way), and set the data onto our attribute.
        //$productModel = $this->productFactory->create()->load($product->getId());
        $extensionAttributes = $product->getExtensionAttributes(); /** get current extension attributes from product **/
        $seller = [
        'id' => (int) 10,
        'name' => 'seller name',
        'image' => null
    ];
        $extensionAttributes->setSeller($seller);
        $product->setExtensionAttributes($extensionAttributes);
        return $product;
    }

    public function afterGetList(
        \Magento\Catalog\Api\ProductRepositoryInterface $subject,
        \Magento\Catalog\Api\Data\ProductSearchResultsInterface $searchCriteria
    ) : \Magento\Catalog\Api\Data\ProductSearchResultsInterface
    {
        $products = [];
        foreach ($searchCriteria->getItems() as $entity) {
            /** @var ProductInterface $product */
            // Fetch the raw product model (I have not found a better way), and set the data onto our attribute.
            //$productModel = $this->productFactory->create()->load($product->getId());
            $extensionAttributes = $entity->getExtensionAttributes(); /** get current extension attributes from product **/
            $seller = [
        'id' => (int) 10,
        'name' => 'seller name',
        'image' => null
    ];
            $extensionAttributes->setSeller($seller);
            $entity->setExtensionAttributes($extensionAttributes);

            $products[] = $entity;
        }
        $searchCriteria->setItems($products);
        return $searchCriteria;
    }
}

But the result for product list is null:

{
    "status_code": 200,
    "reason_phrase": "OK",
    "body": null
}

So any suggestion about that please?