Service/CheckerManager.php
public function getSelectedHeaderChecker(array $selected_header_checkers)
    {
        $result = [];
        foreach ($selected_header_checkers as $alias) {
            Assertion::keyExists($this->header_checkers, $alias, sprintf('The header checker alias "%s" is not supported.', $alias));
            $result[] = $this->header_checkers[$alias];
        }

        return $result;
    }
public function getSelectedHeaderChecker(array $selected_header_checkers)
    {
        $result = [];
        foreach ($selected_header_checkers as $alias) {
            Assertion::keyExists($this->header_checkers, $alias, sprintf('The header checker alias "%s" is not supported.', $alias));
            $result[] = $this->header_checkers[$alias];
        }

        return $result;
    }
@param string[] $selected_header_checkers

@return \Jose\Checker\HeaderCheckerInterface[]