Controller/Adminhtml/FastlyCdn/Manifest/GetCountries.php
public function execute()
    {
        $result = $this->resultJson->create();
        try {
            $countries = $this->countryHelper->toOptionArray();
            if (!$countries) {
                return $result->setData([
                    'status'    => false,
                    'msg'       => 'Could not fetch list countries.'
                ]);
            }

            return $result->setData([
                'status'    => true,
                'countries'  => $countries
            ]);
        } catch (\Exception $e) {
            return $result->setData([
                'status'    => false,
                'msg'       => $e->getMessage()
            ]);
        }
    }
public function execute()
    {
        $result = $this->resultJson->create();
        try {
            $countries = $this->countryHelper->toOptionArray();
            if (!$countries) {
                return $result->setData([
                    'status'    => false,
                    'msg'       => 'Could not fetch list countries.'
                ]);
            }

            return $result->setData([
                'status'    => true,
                'countries'  => $countries
            ]);
        } catch (\Exception $e) {
            return $result->setData([
                'status'    => false,
                'msg'       => $e->getMessage()
            ]);
        }
    }
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@return $this|ResponseInterface|ResultInterface