Fatal error: Uncaught Error: Undefined class constant 'CACHE_TAG' in
C:xampphtdocstest-localappcodeTestingSimpleNewsModelNews.php:9
Stack trace: #0 C:xampphtdocstest-localvendormagentoframeworkAppCacheTagStrategyIdentifier.php(25):TestingSimpleNewModeNews->getIdentities()
#1 C:xampphtdocstest-localvendormagentoframeworkAppCacheTagResolver.php(43): MagentoFrameworkAppCacheTagStrategyIdentifier->getTags(Object(TestingSimpleNewsModelNews))
#2 C:xampphtdocstest-localvendormagentomodule-page-cacheObserverFlushCacheByTags.php(64): MagentoFrameworkAppCacheTagResolver->getTags(Object(TestingSimpleNewsModelNews))
#3 C:xampphtdocstest-localvendormagentoframeworkEventInvokerInvokerDefault.php(72): MagentoPageCacheObserverFlushCacheByTags->execute(Object(MagentoFrameworkEventObserver))
#4 C:xampphtdocstest-localvendormagentoframeworkEventInvokerInvokerDefault.php(60): MagentoFrameworkEventInvokerInvokerDefault->_callObserverMethod(Object(Magento in C:xampphtdocstest-localappcodeTestingSimpleNewsModelNews.php on line 9

<?php

namespace TestingSimpleNewsModel;

class News extends MagentoFrameworkModelAbstractModel implements MagentoFrameworkDataObjectIdentityInterface
{
    public function getIdentities()
    {
        return [self::CACHE_TAG . '_' . $this->getId()];
    }

    public function getDefaultValues()
    {
        $values = [];

        return $values;
    }

    /**
     * Define resource model
     */
    protected function _construct()
    {
        $this->_init('TestingSimpleNewsModelResourceNews');
    }
}