Webmozart\Assert\Assert::notNull PHP Method

    public static function notNull($value, $message = '')
    {
        if (null === $value) {
            static::reportInvalidArgument($message ?: 'Expected a value other than null.');
        }
    }

 /**
  * {@inheritdoc}
  */
 public function calculate(ProductVariantInterface $productVariant, array $context)
 {
     Assert::keyExists($context, 'channel');
     $channelPricing = $productVariant->getChannelPricingForChannel($context['channel']);
     Assert::notNull($channelPricing);
     return $channelPricing->getPrice();
 }